Sentiment Analysis: nearly everything you need to know

Sentiment analysis is the automated process of understanding an opinion about a given subject from written or spoken language.

In a world where we generate 2.5 quintillion bytes of data every day, sentiment analysis has become a key tool for making sense of that data. This has allowed companies to get key insights and automate all kind of processes.

But… How does it work?

What are the different approaches? What are its caveats and limitations? How can you use sentiment analysis in your business?

Below, you’ll find the answers to these questions and everything you need to know about sentiment analysis. No matter if you are an experienced data scientist, a developer, a marketer, a product analyst, or if you’re just getting started with text analysis, this comprehensive guide is for you.

Read along, bookmark it for later, or jump to the sections of your interest. This guide is divided into four sections:

Let’s get started!

The Basics of Sentiment Analysis

The Basics of Sentiment Analysis

What is Sentiment Analysis?

Sentiment Analysis also known as Opinion Mining is a field within Natural Language Processing (NLP) that builds systems that try to identify and extract opinions within text. Usually, besides identifying the opinion, these systems extract attributes of the expression e.g.:

  • Polarity: if the speaker express a positive or negative opinion,
  • Subject: the thing that is being talked about,
  • Opinion holder: the person, or entity that expresses the opinion.

Currently, sentiment analysis is a topic of great interest and development since it has many practical applications. Since publicly and privately available information over Internet is constantly growing, a large number of texts expressing opinions are available in review sites, forums, blogs, and social media.

With the help of sentiment analysis systems, this unstructured information could be automatically transformed into structured data of public opinions about products, services, brands, politics, or any topic that people can express opinions about. This data can be very useful for commercial applications like marketing analysis, public relations, product reviews, net promoter scoring, product feedback, and customer service.

What Is an Opinion?

Before going into further details, let's first give a definition of opinion. Text information can be broadly categorized into two main types: facts and opinions. Facts are objective expressions about something. Opinions are usually subjective expressions that describe people’s sentiments, appraisals, and feelings toward a subject or topic.

Sentiment analysis, just as many other NLP problems, can be modeled as a classification problem where two sub-problems must be resolved:

  • Classifying a sentence as subjective or objective, known as subjectivity classification.
  • Classifying a sentence as expressing a positive, negative or neutral opinion, known as polarity classification.

In an opinion, the entity the text talks about can be an object, its components, its aspects, its attributes, or its features. It could also be a product, a service, an individual, an organization, an event, or a topic. As an example, take a look at the opinion below:

"The battery life of this camera is too short."

A negative opinion is expressed about a feature (battery life) of an entity (camera).

Direct vs Comparative Opinions

There are two kinds of opinions: direct and comparative. Direct opinions give an opinion about a entity directly, for example:

"The picture quality of camera A is poor."

This direct opinion states a negative opinion about camera A.

In comparative opinions, the opinion is expressed by comparing an entity with another, for example:

“The picture quality of camera A is better than that of camera B.”

Usually, comparative opinions express similarities or differences between two or more entities using a comparative or superlative form of an adjective or adverb. In the previous example, there's a positive opinion about camera A and, conversely, a negative opinion about camera B.

Explicit vs Implicit Opinions

An explicit opinion on a subject is an opinion explicitly expressed in a subjective sentence. The following sentence expresses an explicit positive opinion:

“The voice quality of this phone is amazing.”

An implicit opinion on a subject is an opinion implied in an objective sentence. The following sentence expresses an implicit negative opinion:

“The earphone broke in two days.”

Within implicit opinions we could include metaphors that may be the most difficult type of opinions to analyze as they include a lot of semantic information.

Sentiment Analysis Scope

Sentiment analysis can be applied at different levels of scope:

  • Document level sentiment analysis obtains the sentiment of a complete document or paragraph.
  • Sentence level sentiment analysis obtains the sentiment of a single sentence.
  • Sub-sentence level sentiment analysis obtains the sentiment of sub-expressions within a sentence.

Types of Sentiment Analysis

There are many types and flavors of sentiment analysis and SA tools range from systems that focus on polarity (positive, negative, neutral) to systems that detect feelings and emotions (angry, happy, sad, etc) or identify intentions (e.g. interested v. not interested). In the following section, we’ll cover the most important ones.

Fine-grained Sentiment Analysis

Sometimes you may be also interested in being more precise about the level of polarity of the opinion, so instead of just talking about positive, neutral, or negative opinions you could consider the following categories:

  • Very positive
  • Positive
  • Neutral
  • Negative
  • Very negative

This is usually referred to as fine-grained sentiment analysis. This could be, for example, mapped onto a 5-star rating in a review, e.g.: Very Positive = 5 stars and Very Negative = 1 star.

Some systems also provide different flavors of polarity by identifying if the positive or negative sentiment is associated with a particular feeling, such as, anger, sadness, or worries (i.e. negative feelings) or happiness, love, or enthusiasm (i.e. positive feelings).

Emotion detection

Emotion detection aims at detecting emotions like, happiness, frustration, anger, sadness, and the like. Many emotion detection systems resort to lexicons (i.e. lists of words and the emotions they convey) or complex machine learning algorithms.

One of the downsides of resorting to lexicons is that the way people express their emotions varies a lot and so do the lexical items they use. Some words that would typically express anger like shit or kill (e.g. in your product is a piece of shit or your customer support is killing me) might also express happiness (e.g. in texts like This is the shit or You are killing it).

Aspect-based Sentiment Analysis

Usually, when analyzing the sentiment in subjects, for example products, you might be interested in not only whether people are talking with a positive, neutral, or negative polarity about the product, but also which particular aspects or features of the product people talk about. That's what aspect-based sentiment analysis is about. In our previous example:

"The battery life of this camera is too short."

The sentence is expressing a negative opinion about the camera, but more precisely, about the battery life, which is a particular feature of the camera.

Intent analysis

Intent analysis basically detects what people want to do with a text rather than what people say with that text. Look at the following examples:

“Your customer support is a disaster. I’ve been on hold for 20 minutes”.

“I would like to know how to replace the cartridge”.

“Can you help me fill out this form?”

A human being has no problems detecting the complaint in the first text, the question in the second text, and the request in the third text. However, machines can have some problems to identify those. Sometimes, the intended action can be inferred from the text, but sometimes, inferring it requires some contextual knowledge.

Multilingual sentiment analysis

Multilingual sentiment analysis can be a difficult task. Usually, a lot of preprocessing is needed and that preprocessing makes use of a number of resources. Most of these resources are available online (e.g. sentiment lexicons), but many others have to be created (e.g. translated corpora or noise detection algorithms). The use of the resources available requires a lot of coding experience and can take long to implement.

An alternative to that would be detecting language in texts automatically, then train a custom model for the language of your choice (if texts are not written in English), and finally, perform the analysis.

Why sentiment analysis is important?

It’s estimated that 80% of the world’s data is unstructured and not organized in a pre-defined manner. Most of this comes from text data, like emails, support tickets, chats, social media, surveys, articles, and documents. These texts are usually difficult, time-consuming and expensive to analyze, understand, and sort through.

Sentiment analysis systems allows companies to make sense of this sea of unstructured text by automating business processes, getting actionable insights, and saving hours of manual data processing, in other words, by making teams more efficient.

Some of the advantages of sentiment analysis include the following:

Can you imagine manually sorting through thousands of tweets, customer support conversations, or customer reviews? There’s just too much data to process manually. Sentiment analysis allows to process data at scale in a efficient and cost-effective way.

We can use sentiment analysis to identify critical information that allows situational awareness during specific scenarios in real-time. Is there a PR crisis in social media about to burst? An angry customer that is about to churn? A sentiment analysis system can help you immediately identify these kinds of situations and take action.

Humans don’t observe clear criteria for evaluating the sentiment of a piece of text. It’s estimated that different people only agree around 60-65% of the times when judging the sentiment for a particular piece of text. It’s a subjective task which is heavily influenced by personal experiences, thoughts, and beliefs. By using a centralized sentiment analysis system, companies can apply the same criteria to all of their data. This helps to reduce errors and improve data consistency.

Check out the Use Cases & Applications section to see examples of companies and organizations that are using sentiment analysis for a diverse set of things.

How Does Sentiment Analysis Work?

How Does Sentiment Analysis Work?

Sentiment Analysis Algorithms

There are many methods and algorithms to implement sentiment analysis systems, which can be classified as:

  • Rule-based systems that perform sentiment analysis based on a set of manually crafted rules.
  • Automatic systems that rely on machine learning techniques to learn from data.
  • Hybrid systems that combine both rule based and automatic approaches.

Rule-based Approaches

Usually, rule-based approaches define a set of rules in some kind of scripting language that identify subjectivity, polarity, or the subject of an opinion.

The rules may use a variety of inputs, such as the following:

  • Classic NLP techniques like stemming, tokenization, part of speech tagging and parsing.
  • Other resources, such as lexicons (i.e. lists of words and expressions).

A basic example of a rule-based implementation would be the following:

  1. Define two lists of polarized words (e.g. negative words such as bad, worst, ugly, etc and positive words such as good, best, beautiful, etc).
  2. Given a text:
    1. Count the number of positive words that appear in the text.
    2. Count the number of negative words that appear in the text.
  3. If the number of positive word appearances is greater than the number of negative word appearances return a positive sentiment, conversely, return a negative sentiment. Otherwise, return neutral.

This system is very naïve since it doesn't take into account how words are combined in a sequence. A more advanced processing can be made, but these systems get very complex quickly. They can be very hard to maintain as new rules may be needed to add support for new expressions and vocabulary. Besides, adding new rules may have undesired outcomes as a result of the interaction with previous rules. As a result, these systems require important investments in manually tuning and maintaining the rules.

Automatic Approaches

Automatic methods, contrary to rule-based systems, don't rely on manually crafted rules, but on machine learning techniques. The sentiment analysis task is usually modeled as a classification problem where a classifier is fed with a text and returns the corresponding category, e.g. positive, negative, or neutral (in case polarity analysis is being performed).

Said machine learning classifier can usually be implemented with the following steps and components:

Automatic Approaches for Sentiment analysis

The Training and Prediction Processes

In the training process (a), our model learns to associate a particular input (i.e. a text) to the corresponding output (tag) based on the test samples used for training. The feature extractor transfers the text input into a feature vector. Pairs of feature vectors and tags (e.g. positive, negative, or neutral) are fed into the machine learning algorithm to generate a model.

In the prediction process (b), the feature extractor is used to transform unseen text inputs into feature vectors. These feature vectors are then fed into the model, which generates predicted tags (again, positive, negative, or neutral).

Feature Extraction from Text

The first step in a machine learning text classifier is to transform the text into a numerical representation, usually a vector. Usually, each component of the vector represents the frequency of a word or expression in a predefined dictionary (e.g. a lexicon of polarized words). This process is known as feature extraction or text vectorization and the classical approach has been bag-of-words or bag-of-ngrams with their frequency.

More recently, new feature extraction techniques have been applied based on word embeddings (also known as word vectors). This kind of representations makes it possible for words with similar meaning to have a similar representation, which can improve the performance of classifiers.

Classification Algorithms

The classification step usually involves a statistical model like Naïve Bayes, Logistic Regression, Support Vector Machines, or Neural Networks:

  • Naïve Bayes: a family of probabilistic algorithms that uses Bayes’s Theorem to predict the category of a text.

  • Linear Regression: a very well-known algorithms in statistics used to predict some value (Y) given a set of features (X).

  • Support Vector Machines: a non-probabilistic model which uses a representation of text examples as points in a multidimensional space. These examples are mapped so that the examples of the different categories (sentiments) belong to distinct regions of that space.. Then, new texts are mapped onto that same space and predicted to belong to a category based on which region they fall into.

  • Deep Learning: a diverse set of algorithms that attempts to imitate how the human brain works by employing artificial neural networks to process data.

Sentiment Analysis Metrics and Evaluation

There are many ways in which you can obtain performance metrics for evaluating a classifier and to understand how accurate a sentiment analysis model is. One of the most frequently used is known as cross-validation.

What cross-validation does is splitting the training data into a certain number of training folds (with 75% of the training data) and a the same number of testing folds (with 25% of the training data), use the training folds to train the classifier, and test it against the testing folds to obtain performance metrics (see below). The process is repeated multiple times and an average for each of the metrics is calculated.

If your testing set is always the same, you might be overfitting to that testing set, which means you might be adjusting your analysis to a given set of data so much that you might fail to analyze a different set. Cross-validation helps prevent that. The more data you have, the more folds you will be able to use.

Precision, Recall, and Accuracy

Precision, recall, and accuracy are standard metrics used to evaluate the performance of a classifier.

Precision measures how many texts were predicted correctly as belonging to a given category out of all of the texts that were predicted (correctly and incorrectly) as belonging to the category.

Recall measures how many texts were predicted correctly as belonging to a given category out of all the texts that should have been predicted as belonging to the category. We also know that the more data we feed our classifiers with, the better recall will be.

Accuracy measures how many texts were predicted correctly (both as belonging to a category and not belonging to the category) out of all of the texts in the corpus.

Most frequently, precision and recall are used to measure performance since accuracy alone does not say much about how good or bad a classifier is.

For a difficult task like analyzing sentiment, precision and recall levels are likely to be low at first. As you feed the classifier with more data, performance will improve. However, as we will see below, since annotated data is not likely to be accurate, the chances are that precision levels won’t get too high. However, if you feed the classifier consistently tagged data, results are going to be as good as results can be for any other classification problem.

Inter-annotator agreement

When it comes to inter-annotator agreement (i.e. agreement by humans on a given annotation task), one of the most frequently used metrics is Krippendorff’s Alpha. According to Saif et al., best inter-annotator agreement for Twitter sentiment analysis reaches a 0.655 value of Krippendorff’s Alpha. This means there is a good deal of agreement (since alpha is greater than zero), but we believe it’s still far from great (e.g.: around 0.8, which is the minimum reliability threshold social scientists use in order to say data is reliable, see here). This said, only tentative conclusions about the sentiment of tweets can be drawn from the results of the annotation tasks described in the paper cited above.

All in all, what this 0.655 is an indicator of the difficulty of sentiment analysis detection for humans as well. Taking into consideration that machines learn from the data they are fed with, automatic predictions are likely to mirror the human disagreement embedded in the data.

Hybrid Approaches

The concept of hybrid methods is very intuitive: just combine the best of both worlds, the rule-based and the automatic ones. Usually, by combining both approaches, the methods can improve accuracy and precision.

Sentiment Analysis Challenges

Most of the work in sentiment analysis in recent years has been around developing more accurate sentiment classifiers by dealing with some of the main challenges and limitations in the field.

The detection of subjective and objective texts is just as important as analyzing their tone. In fact, so called objective texts do not contain explicit sentiments. Say, for example, you intend to analyze the sentiment of the following two texts:

The package is nice.

The package is red.

Most people would say that sentiment is positive for the first one and neutral for the second one, right? All predicates (adjectives, verbs, and some nouns) should not be treated the same with respect to how they create sentiment. In the examples above, nice is more subjective than red.

Context and Polarity

All utterances are uttered at some point in time, in some place, by and to some people, you get the point. All utterances are uttered in context. Analyzing sentiment without context gets pretty difficult. However, machines cannot learn about contexts if they are not mentioned explicitly. One of the problems that arise from context is changes in polarity. Look at the following responses to a survey:

Everything of it.

Absolutely nothing!

Imagine the responses above come from answers to the question What did you like about the event? The first response would be positive and the second one would be negative, right? Now, imagine the responses come from answers to the question What did you DISlike about the event? The negative in the question will make sentiment analysis change altogether.

A good deal of preprocessing or postprocessing will be needed if we are to take into account at least part of the context in which texts were produced. However, how to preprocess or postprocess data in order to capture the bits of context that will help analyze sentiment is not straightforward.

Irony and Sarcasm

Differences between literal and intended meaning (i.e. irony) and the more insulting or ridiculizing version of irony (i.e. sarcasm) usually change positive sentiment into negative whereas negative or neutral sentiment might be changed to positive. However, detecting irony or sarcasm takes a good deal of analysis of the context in which the texts are produced and, therefore, are really difficult to detect automatically.

For example, look at some possible answers to the question Have you had a nice customer experience with us? below.

Yeah. Sure.

Not one, but many!

What sentiment would you assign to the responses above? Probably, you have listened to the first response so many times, you would have said negative, right? The problem is there is no textual cue that will make a machine learn that negative sentiment since most often, yeah and sure belong to positive or neutral texts.

How about the second response? In this context, sentiment is positive, but we’re sure you can come up with many different contexts in which the same response can express negative sentiment.


How to treat comparisons in sentiment analysis is another challenge worth tackling. Look at the texts below:

This product is second to none.

This is better than old tools.

This is better than nothing.

There are some comparisons like the first one above that do not need any contextual clues in order to be classified correctly.

The second and third texts are a little more difficult to classify, though. Would you classify them as neutral or positive? Probably, you are more likely to choose positive for the second one and neutral for the third, right? Once again, context can make a difference. For example, if the old tools the second text talks about were considered useless in context, then the second text turns out to be pretty similar to the third text. However, if no context is provided, these texts feel different.


There are two types of emojis according to Guibon et al.. Western emojis (e.g. :D) are encoded in only one character or in a combination of a couple of them whereas Eastern emojis (e.g. ¯ \ _ (ツ) _ / ¯) are a longer combination of characters of a vertical nature. Particularly in tweets, emojis play a role in the sentiment of texts.

Sentiment analysis performed over tweets requires special attention to character-level as well as word-level. However, no matter how much attention you pay to each of them, a lot of preprocessing might be needed. For example, you might want to preprocess social media content and transform both Western and Eastern emojis into tokens and whitelist them (i.e. always take them as a feature for classification purposes) in order to help improve sentiment analysis performance.

Here’s a quite comprehensive list of emojis and their unicode characters that may come in handy when preprocessing.

Defining Neutral

Defining what we mean by neutral is another challenge to tackle in order to perform accurate sentiment analysis. As in all classification problems, defining your categories -and, in this case, the neutral tag- is one of the most important parts of the problem. What you mean by neutral, positive, or negative does matter when you train sentiment analysis models. Since tagging data requires that tagging criteria be consistent, a good definition of the problem is a must.

Here’s some ideas on what a neutral tag might contain:

  1. Objective texts. As we say here, so called objective texts do not contain explicit sentiments, so you should include those texts into the neutral category.
  2. Irrelevant information. If you haven’t preprocessed your data to filter out irrelevant information, you can tag it neutral. However, be careful! Only do this if you know how this could affect overall performance. Sometimes, you will be adding noise to your classifier and performance could get worse.
  3. Texts containing wishes. Some wishes like I wish the product had more integrations are generally neutral. However, those including comparisons, like I wish the product were better are pretty difficult to categorize

How Accurate Is Sentiment Analysis?

Here’s what sentiment analysis is: it’s a tremendously difficult task even for human beings. That said, sentiment analysis classifiers might not be as precise as other types of classifiers. Remember that inter-annotator agreement is pretty low and that machines learn from the data they are fed with (see above).

That said, you might be saying, is it worth the effort? The answer is simple: it sure is worth it! Chances are that sentiment analysis predictions will be wrong from time to time, but by using sentiment analysis you will get the opportunity to get it right about 70-80% of the times you submit your texts for classification.

If you or your company have not used sentiment analysis before, then you’ll see some improvement really quickly. For typical use cases, such as ticket routing, brand monitoring, and VoC analysis (see below), this means you will save a lot of time and money -which you are likely to be investing in in-house manual work nowadays,- save your teams some frustration, and increase your (or your company’s) productivity.

Sentiment Analysis Use Cases & Applications

Sentiment Analysis Use Cases & Applications

In this section, we’ll take a dive into real life use cases, applications, and examples of the impact of all this can have on businesses, cities, and society – sentiment analysis in the wild, if you will.

Specifically, we’ll examine the use of sentiment analysis in the following:

  • Social media monitoring
  • Brand monitoring
  • Voice of customer (VoC)
  • Customer service
  • Workforce analytics and voice of employee
  • Product analytics
  • Market research and analysis

On the fateful evening of April 9th, 2017, United Airlines forcibly removed a passenger from an overbooked flight. The nightmare-ish incident was filmed by other passengers on their smartphones and posted immediately. One such video, posted to Facebook, was shared more than 87,000 times and viewed 6.8 million times by 6pm on Monday, just 24 hours later.

The fiasco was magnified horrifically by the company’s dismissive response. On Monday afternoon, they tweeted a statement from the CEO apologizing for “having to re-accommodate customers.” Cue public outrage –you can imagine the field day on Twitter.

This is exactly the kind of PR catastrophe we’d all like to do happily without. This is also an excellent example of why we care not only about if people are talking about our brand, but how they’re talking about it. More mentions does not equal positive mentions.

In today’s day and age, brands of all shapes and sizes have meaningful interactions with customers, leads, and even competition on social networks like Facebook, Twitter, and Instagram. Most marketing departments are already tuned into to online mentions as far as volume –they measure more chatter as more brand awareness. Nowadays, however, we can take a step deeper. By using sentiment analysis on social media, we can get incredible insights into the quality of conversation that’s happening around a brand.

How Sentiment Analysis Can Be Used

  • Analyze tweets and/or facebook posts over a period of time to see sentiment of a particular audience.
  • Run sentiment analysis on all social media mentions to your brand and automatically categorize by urgency.
  • Automatically route social media mentions to team members best fit to respond.
  • Automate any or all of these processes.
  • Use analytics to gain deep insight into what’s happening across your social media channels.

Top Benefits

Sentiment analysis is useful in social media monitoring because it helps you do all of the following:

  • Prioritize action. Which is more urgent: a fuming customer or a subtle “thanks!” shout-out? Obviously the fumer. Sentiment analysis lets you easily filter unread mentions by positivity and negativity, showing you which blazing fires to put on the “extinguish immediately” list and which slow smolders can wait a bit.
  • Track trends over time.
  • Tune into a specific point in time –i.e. the lead-up to a new product launch or the day a particular piece of bad press dropped.
  • Keep a finger on the competition. Why not monitor your competitors’ social media the same way you monitor your own? If you tune in closely, maybe you notice there’s been a negative response to a particular feature of their new product, and you respond by designing a lead generation campaign targeting exactly that gap. They won’t even know what hit them.

Example: Trump vs Clinton, according to Twitter

Over the course of a few months during the 2016 US Presidential Elections, we collected and analyzed millions of tweets mentioning Clinton or Trump posted by users from around the world. We classified each of those tweets with a sentiment of either positive, neutral, or negative.

For example:

  • Negative: “Racial discord was conceived, nurtured, refined & perpetuated by Americans incl @realDonaldTrump’s father. Get real!”
  • Neutral: “@HillaryClinton will receive the first question at tonight’s presidential debate, according to @CBSNews #ClintonVsTrump”.
  • Positive: “Americans trust @realDonaldTrump to Make our Economy Great Again!”
  • Positive: “@wcve it’s amazing how our city loves him and he really loves our city. @HillaryClinton made a great choice for Vice President. @timkaine”.

From this simple, easy analysis, we found interesting insights:

  • More tweets mentioned @realDonaldTrump (~450k/day) than @HillaryClinton (~250k/day). Again, this does not equal positivity, but does imply brand awareness (and in the case of something like elections, awareness is key).
  • For both candidates, there were more negative than positive tweets. Given that it’s Twitter and politics, this was not much of a surprise.
  • Trump had a better positive to negative Tweet ratio than Clinton.

To sum up, more people were tweeting about Trump, and a higher percentage of the people tweeting about Trump were doing so more positively than were the people tweeting about Clinton.

Sentiment Analysis in Brand Monitoring

Not only do brands have a wealth of information available on social media, but they also can look more broadly across the internet to see how people are talking about them online. Instead of focusing on specific social media platforms such as Facebook and Twitter, we can target mentions in places like news, blogs, and forums –again, looking at not just the volume of mentions, but also the quality of those mentions.

In our United Airlines example, for instance, the flare-up started on the social media platforms of a few passengers. Within hours, it was picked up by news sites and spread like wildfire across the US. News then spread to China and Vietnam, as the passenger was reported to be an American of Chinese-Vietnamese descent and people accused the perpetrators of racial profiling. In China, the incident became the number one trending topic on Weibo, a microblogging site with almost 500 million users.

And again, this is all happening within mere hours and days of when the incident took place.

How Sentiment Analysis Can Be Used

  • Analyze news articles, blog posts, forum discussions, and other texts on the internet over a period of time to see sentiment of a particular audience.
  • Automatically categorize urgency of all online mentions to your brand via sentiment analysis.
  • Automatically alert designated team members of online mentions that concern their area of work.
  • Automate any or all of these processes.
  • Better understand a brand online presence by getting all kinds of interesting insights and analytics.

Top Benefits

Sentiment analysis is useful in brand monitoring because it helps you do all of this:

  • Understand how your brand reputation evolves over time.
  • Research your competition and understand how their reputation also evolves over time.
  • Identify potential PR crises and know to take immediate action. Again, prioritize what fires need to be put out immediately and what mentions can wait.
  • Tune into a specific point in time. Again, maybe you want to look at just press mentions on the day of your IPO filing, or a new product launch. Sentiment analysis lets you do that.

Example: Expedia Canada

Around Christmastime, Expedia Canada ran a classic “escape winter” marketing campaign. All was well, except for their choice of screeching violin as background music. Understandably, people took to social media, blogs, and forums. Expedia noticed that and removed the ad. Then, they created a series of follow-up spin-off videos: one showed the original actor smashing the violin, and in another one, they invited a real follower who had complained on Twitter to come in and rip the violin away. Though their original product was far from flawless, they were able to redeem themselves by incorporating real customer feedback into continued iterations.

Using sentiment analysis (and machine learning), you can automatically monitor all chatter around your brand and detect this type of potentially-explosive scenario while you still have time to defuse it.

Sentiment Analysis in Customer Feedback

Social media and brand monitoring offer us immediate, unfiltered, invaluable information on customer sentiment. In a parallel vein run two other troves of insight –surveys and customer support interactions. Teams often look at their Net Promoter Score (NPS), but we can also apply this analyses to any type of survey or communication channel that yields textual customer feedback.

NPS surveys ask a few simple questions – namely, Would you recommend this company, product, and/or service to a friend or family member? and why? –and use that to identify customers as promoters, passives, or detractors. The goal is to identify overall customer experience, and find ways to elevate all customers to “promoter” level, where they theoretically will buy more, stay longer, and refer other customers.

Numerical survey data is easily aggregated and assessed, but we want that same ease with the “why” answers as well. A regular NPS score simply gives you a number, without the additional context of what it’s about and why the score landed there. Sentiment analysis takes it that step further.

How Sentiment Analysis Can Be Used:

  • Analyze aggregated NPS or other survey responses.
  • Analyze aggregated customer support interactions.
  • Track customer sentiment about specific aspects of the business over time. This adds depth to explain why the overall NPS score might have changed, or if specific aspects have shifted independently.
  • Target individuals to improve their service. By automating sentiment analysis on incoming surveys, you can be alerted to customers who feel strongly negatively towards your product or service, and can deal with them specifically.
  • Determine if particular customer segments feel more strongly about your company. You can zero in on sentiment by certain demographics, interests, personas, etc.

Top Benefits:

Sentiment analysis is useful in understanding Voice of Customer (VoC) because it helps you do all of the following:

  • Use results of sentiment analysis to design better informed questions to ask on future surveys.
  • Understand the nuances of customer experience over time, along with why and how shifts are happening.
  • Empower your internal teams by giving them a deeper view of the customer experience, by segment and by specific aspects of the business.
  • Respond more quickly to signals and shifts from customers.

Example: McKinsey City Voices project

In Brazil, federal public spending rose by 156% from 2007 to 2015 while people’s satisfaction with public services steadily decreased. Unhappy with this counterproductive progress, the Urban-planning Department recruited McKinsey to help them work on a series of new projects that would focus first on user experience, or citizen journeys, when delivering services. This citizen-centric style of governance has led to the rise of what we call Smart Cities.

McKinsey developed a tool called City Voices, which conducts citizen (customer) surveys across more than 150 different metrics, and then runs sentiment analysis to help leaders understand how constituents live and what they need, in order to better inform public policy. By using this tool, the Brazilian government was able to surface urgent needs –a safer bus system, for instance– and improve them first.

If even whole cities and countries, famous for their red tape and slow pace, are incorporating customer journeys and sentiment analysis into their decision making processes, then innovative companies better be far ahead.

Sentiment Analysis in Customer Support

We all know the drill: stellar customer experiences = more probable returning customers. Particularly in recent years, there’s been a lot of talk (rightfully so) around customer experience and customer journeys. Leading companies have begun to realize that oftentimes how they deliver is just as (if not more) important as what they deliver. Nowadays, more than ever, customers expect their experience with companies to be immediate, intuitive, personal, and hassle-free. In fact, research shows that 25% of customers will switch to a competitor after just one negative interaction.

We already looked at how we can use sentiment analysis in looking at the broader VoC, but now we’ll dial in on specifically customer service teams.

How Sentiment Analysis Can Be Used:

  • Automate systems to run sentiment analysis on all incoming customer support queries.
  • Rapidly detect disgruntled customers and surface those tickets to the top.
  • Route queries to specific team members best suited to respond.
  • Use analytics to gain deep insight into what’s happening across your customer support.

Top Benefits

Sentiment analysis is useful in customer support because it helps you do all of this:

  • Prioritize order for responding to tickets, being sure to address the most urgent needs first.
  • Increase efficiency by automatically assigning tickets to a particular category or team member.

Example: Analyzing customer support interactions on Twitter

Just for kicks, we decided to do some analysis on how the four biggest US phone carriers (AT&T, Verizon, Sprint, and T-Mobile) handled customer support interactions on Twitter. We downloaded tens of thousands of tweets mentioning the companies (by name or by handle), and ran them through a MonkeyLearn sentiment model to categorize each tweet as positive, neutral, or negative. We then used our new Insight Extractor, which reads all text as one unit, extracts the most relevant keywords, and returns the most relevant sentences including each keyword.

Here’s some insights:

  • T-Mobile had far and away the highest percentage of positive tweets.
  • Verizon was the only company with more negative tweets than positive ones.
  • Top keywords for positive tweets at Verizon included typical terms such as “new phone,” “thanks,” and “quality customer service.” Key sentences were typical, formal, somewhat dry interactions between the team and followers.
  • Top keywords for positive tweets at T-Mobile included names of people on their customer support team, because their team runs higher engagement, back-and-forth about anything type conversations with followers.

To sum up, this could imply that a more personal, engaging take on social media elicits more positive responses and higher customer satisfaction.

Sentiment Analysis in Workforce Analytics & Voice of the Employee

In the same way we measure VoC via customer surveys, we can solicit and act on feedback from our own employees. Chances are they are wildly more invested in giving actionable ideas on how to improve the workplace. And chances are that you, as the employer, are wildly more interested in keeping them engaged and empowered to do their best.

How Sentiment Analysis Can Be Used:

  • Analyze employee surveys, extract keywords, and view by segment.
  • Track changes in employee sentiment over time.
  • Surface urgent concerns immediately.

Top Benefits:

Sentiment analysis is useful in workplace analytics and VoE because it helps you do the following:

  • Discover and address employee concerns, ensuring they feel heard and valued.
  • Understand VoE in real-time, rather than annual surveys or performance reviews.


Let’s say you conduct an internal survey asking employees to rate various aspects of their workplace experience and explain why they feel that way. On a scale of 1 to 10, a top-performing employee may say she rates her engagement at work as a 5 –not ideal. However, if we look closer, we see she added “I love the work I do and my training opportunities have been excellent, but my boss makes occasional inappropriate remarks towards me that make me feel uncomfortable.”

A response like this should raise red flags of potential sexual harassment and be brought immediately to HR’s attention in order to address the situation. If you simply slop it together with the other aggregated scores and don’t read through them for another two months, you risk losing a valuable employee or heightening an already tense situation.

Sentiment Analysis in Product Analytics

In our agile world, we’ve learned that products are best built by prototyping early, soliciting feedback frequently, and continuing to iterate and improve. But for many product teams, soliciting frequent feedback can be the trickiest part. How do you narrow down which customer segment to ask? How do you sort through and weigh all their feedback? This is exactly where sentiment analysis can change the game. Whether by analyzing surveys, customer support interactions, or social media, machine learning enables you to assess huge amounts of product feedback at once.

How Sentiment Analysis Can Be Used:

  • Analyze large quantities of product feedback surveys
  • Analyze all social media and online mentions about a product
  • Filter comments by aspect and by sentiment, in order to see what to tweak and what to keep.
  • Automatically route relevant comments to product teams.

Top Benefits:

Sentiment analysis is useful to product analytics because it helps you do all of the following:

  • Keep constant tabs on what people like and don’t like about your product.
  • Zero in on which segments like which things, and how to appeal to those audiences.
  • Empower your product development team with incredible insight into specifics of product performance.

Example: MonkeyLearn

Our team runs sentiment analysis on customer support interactions and uses those insights to empower everyone in our company –not just our support agents. So when a customer mentions that they’re having difficulty with X or that they’d like to see Y, we feed that information directly to the people who make and manage our products. We had real feedback from real customers, directly reaching the ears of the people to whom it mattered most. As any great product team does, we listen to the customers and meet their needs. All too often, all it takes is simply equipping your team with the right insight.

Sentiment Analysis in Market Research and Analysis

And as a final use case, sentiment analysis empowers all kinds of market research and competitive analysis. Whether you’re exploring a new market, anticipating future trends, or keeping an edge on the competition, sentiment analysis can make all the difference.

How Sentiment Analysis Can Be Used:

  • Analyze product reviews of your brand and compare those with the competition
  • Generate weekly, monthly, or daily reports –a sort of early-warning system
  • Compare sentiment across international markets
  • Analyze formal market reports or business journals for long-term, broader trends
  • Analyze tweets and social media posts for real-time happenings
  • Analyze reviews for unfiltered customer feedback
  • Use aspect-based sentiment analysis to gain rich insight into the details and the reason for otherwise opaque market trends

Top Benefits

Sentiment analysis is useful in market research and analysis because it helps you:

  • Tap into new sources of information.
  • Quantify otherwise qualitative information.
  • Add that qualitative dimension to already-gathered quantitative insights.
  • Provide information in real-time rather than in retrospect.
  • Automated for regular (perhaps weekly) reports.
  • Fill in gaps where public data is scarce –in emerging markets, for instance.

Examples: Hotel reviews on TripAdvisor

Our team was curious about how people feel about hotels in several major cities around the world, so we scraped and analyzed more than one million reviews from TripAdvisor. We looked at hotels in London, Paris, New York, Bangkok, Madrid, Beijing, and Rio de Janeiro.

Here’s some insights:

  • Reviews were mostly positive –on average, 82% of the things people wrote were tagged with a positive sentiment:
  • London hotels got the worst reviews.
  • London was reviewed as dirtier than New York and with the worst food overall.

We used the keyword extraction module to analyze the actual content of the positive/negative reviews, and found a few more interesting insights:

  • “Cockroaches” appears only in Bangkok –watch out!
  • “Croissants” appears only in Paris (as we might expect). Shockingly, though, they appear to be a letdown –reviewed almost exclusively in a negative context. With a closer dive, we saw that was more a reflection on the subpar hotel breakfast food than on the city itself (phew!).

Sentiment Analysis Resources

Sentiment Analysis Resources

Where to Start with Sentiment Analysis

Let’s say that you recently heard about sentiment analysis and it sounded like magic: automatically understanding if a particular message is speaking good or bad about something. You feel inspired thinking about the different applications of this technology.

Now, you want to know more about sentiment analysis, go deeper and explore the different ideas that you may have. But, the thing is you don’t really know where to start or what to do next.

Sentiment analysis is a really vast topic and sometimes beginners can feel overwhelmed on how to get started. There is a very large number of resources out there, from super useful tutorials to all kinds of courses, articles, and papers specialized on this topic.

In this section, our goal is to give a brief overview on different materials and resources to get you started with sentiment analysis.

1) Read the basics

Before diving into the sentiment analysis literature and tutorials, make sure you understand the very basics of sentiment analysis:

Later on, if you feel courageous, you can explore more advanced sentiment analysis literature.

2) Try out an online demo

A good next step in your journey to learn more about sentiment analysis is to play and experiment with an online demo, a place where you can simply type a message and test the results of the analysis for different expressions.

This is useful for having a first-hand experience on the good, the bad, and the ugly of sentiment analysis. By playing with practical examples, you can quickly understand on what type of expressions sentiment analysis shines and works like a charm. You will also rapidly grasp what the challenges and caveats of this technology are.

3) Start experimenting with a tutorial of your choice

Once you have the basics in place, it's time to get your hands dirty and experiment on the domain you are interested in. To do so, we recommend that you browse through the myriad of tutorials available and pick one within your domain and interests.

Sentiment Analysis Demo

In this section, you can try out different models that were trained using MonkeyLearn for a diverse set of sentiment analysis tasks. Feel free to experiment with different expressions and see how different models behave and make their predictions.

If you get an odd result, it could be because the expression you've used hasn’t been correctly learned by the model (yet). Try entering more words to see how this affects the results.

Additionally, you can use MonkeyLearn to create a custom model for sentiment analysis to get specific results that are tailored to your domain and interest.

Generic Sentiment Analysis

This is a generic sentiment analysis classifier for texts in English. It works well on any kind of texts. If you are not sure about which sentiment analysis model to use, you can use this one.

This model can be used for classifying tweets in English according to their sentiment (i.e. positive, neutral or negative).

This model classifies product reviews and opinions in English as positive or negative according to their sentiment.

This sentiment analysis classifier was trained with data from different hotel review sites to distinguish between good and bad reviews.

This sentiment analysis classifier was trained with data from different restaurant review sites to distinguish between good and bad reviews.

This sentiment analysis model was trained with data from different movie review sites to distinguish between good and bad reviews.

This model was trained with tweets about airlines to identify between positive, neutral, and negative tweets.

There is a sentiment analysis tutorial for almost everyone: coders, non-coders, marketers, data analysts, support agents, salespeople, you name it. In this section, we’ll share a varied selection of tutorials so you can find something right up your alley and get your feet wet with sentiment analysis.

Sentiment Analysis Tutorials for Coders

For those that feel comfortable around code and APIs, you can quickly find all kinds of step-by-step guides and resources. Python is the most common programming language for tutorials about data analysis, machine learning, and NLP (including sentiment analysis) but R is quickly catching up, especially with tutorials that aim at data scientists and statisticians.

Sentiment Analysis of Top 100 Subreddits with Python

This video tutorial provides a step-by-step guide on how to use Python to analyze the top 100 subreddits by the sentiment of their comments.

It starts by explaining how to use Beautiful Soup, one of the most popular Python libraries for web scraping, in order to pull data out of web pages. The author uses this library to scrape this web page to get the names of the top 100 subreddits (subreddits like /r/funny, /r/AskReddit and /r/todayilearned).

Once he gets the names of the subreddits, he uses the Praw library to interact with the Reddit API and extract the comments from these subreddits.

Finally, the author explains how to use TextBlob to perform sentiment analysis on the extracted comments.


Sentiment analysis of Slack reviews using R

Let’s imagine that we're the Slack team and we're looking for an easy, reliable way to get data about users’ feelings about our product. We can turn to online reviews in order to answer some top-of-mind questions.

But, when there are thousands of reviews out there, it can be tough to sort through all this feedback and get the insights we're looking for. There is simply too much feedback to process manually.

With this in mind, this step-by-step guide provides an example of how you might use the MonkeyLearn to conduct a seamless sentiment analysis using R of product reviews.

It analyzes a few thousand reviews of Slack on the product review site Capterra and get some great insights from the data.

Sentiment Analysis of the State of the Union with R

Kaggle is a great resource for all kinds of tutorials related to data science. On this useful tutorial by Rachael Tatman, you can learn how to use R for doing sentiment analysis.

The goal is to analyze the State of the Union, the annual message by the President of the United States to the Congress. This message is an opportunity for the president to inform the US citizens (and the world) on how the government is doing regarding issues that are important to the US.

By analyzing the different messages from these State of the Union speeches, it’s possible to get a lot of interesting insights like how the sentiment has changed over time or what presidents tend to have a more negative or positive speech.

The weapons of choice on this tutorial are the Tidytext package for using a sentiment lexicon and ggplot2 package for creating the different visualizations of our analysis.

As a first step, the author proceeds to tokenize the data, which basically means taking the text from the speeches and breaking it up into its individual words. Then, he compares these tokens against a list of words with associated positive or negative sentiments (a sentiment lexicon) and creates some visualizations using the ggplot package.

At the end of the tutorial, the author provides some exercises that are useful to get some additional practice and a deeper understanding of sentiment analysis.

Sentiment Analysis of Tweets Using NLTK

If you are a Python coder and you want to learn how to train your first text classifier for sentiment analysis, this is a great step-by-step guide. The author uses Natural Language Toolkit NLTK to train a classifier that is able to predict the sentiment of a new tweet.

To get started, the author explains how to extract a list of features from a predefined set of positive and negative tweets. These features are a set of distinctive words that can be used to represent each tweet and are a key part of training a classifier.

Then, you’ll learn how to prepare the training data that contains the labeled feature sets. Finally, he proceeds to train a Naive Bayes classifier, a simple but powerful algorithm that works particularly well with natural language processing problems.

Once it has trained a classifier, the author proceeds to explain how to use this model to classify a new incoming tweet.

Sentiment Analysis on Songs Using R

If you are looking for a more advanced tutorial on sentiment analysis using R, then this tutorial is for you. It’s super fun since it explains how to use the Tidytext package to perform sentiment analysis on Prince’s songs.

The author starts by analyzing basic information such as the lexical diversity of Prince lyrics. Then, it explores different sentiment lexicons (including AFINN, Bing, and NRC) and how well they fit to analyse Prince’s lyrics. Afterwards, it proceeds to explain how to effectively perform sentiment analysis on all of Prince’s songs. Once it has the sentiment, it explores the lyrics sentiment over the years and provides a practical explanation on how bigrams affect sentiment.

This tutorial requires some basic understanding of tidy data since it uses dplyr for data transformation and ggplot2 for visualizations.

Sentiment Analysis of Tweets Using Scikit-learn and Jupyter Notebook

Scikit-learn is a simple and efficient tool for data analysis most often used for data classification, regression, and clustering. It’s one of the most frequently used libraries in machine learning since it’s powerful but accessible to everybody. If you are serious about learning about data analysis and machine learning, this tutorial will help you get started with scikit-learn.

It explain how to train a logistic regression model for sentiment analysis. It starts by showing how to properly set up our environment, including jupyter notebook, an application that allows rapid prototyping and sharing of data-related projects.

Afterwards, the author proceeds to explain how to prepare and vectorize our data with scikit-learn. Finally, it trains a linear classifier and shows how to evaluate the model and calculate the accuracy of the model.

Sentiment Analysis Tutorials for Non-technical People

Until recently, sentiment analysis was a niche technology only accessible to technical people with coding skills and background in machine learning. This is no longer the case thanks to the rise of a variety of tools that can be leveraged to get the data and run sentiment analysis models.

The following are some tutorials that can help you get started with sentiment analysis without a single line of code.

Sentiment Analysis with Excel

While we all know how to crunch numbers with Excel functions, analyzing text in spreadsheets is still a hard and manual process. It takes a lot of time to make sense of the text data to create reports and analyze trends. But luckily, there's a better way. Instead of spending hours going through each row, analyzing each text manually, you can use sentiment analysis with Excel to save time and get more done.

MonkeyLearn’s got your back providing a fast and simple way to achieve this. In just 2 simple steps you can incorporate sentiment analysis right into your Excel spreadsheets.

First, you need to select a sentiment analysis model. You can either use a pre-trained model for sentiment analysis or create your own model with your own data and criteria.

Then, you just need to upload your Excel file to run the sentiment analysis with the selected model. And voilà! MonkeyLearn will return a new Excel file with the original data plus two new columns: one with the sentiment analysis result and another one with the confidence of the result.

Sentiment Analysis with Zapier

Are you interested in doing sentiment analysis of tweets? Getting the sentiment of your emails? Or want to automatically understand if answers from a survey on Typeform are positive or negative? No worries, you can use a tool like Zapier to connect with more than 1,000 apps, get the data that you need, and run your sentiment analysis.

After creating a Zap, you will need to set up the first step (trigger) to get the data for doing the analysis. Zapier provides a vast number of choices you could use to import data from, such as Office 365, Google Sheets, Gmail, Slack, Twitter, Typeform, Evernote, Airtable, Salesforce, and others.

Now that you have the data, you will need to set up the second step of your zap to run the sentiment analysis with MonkeyLearn, an AI platform that allows you to analyze text with machine learning. You can either use pre-trained sentiment analysis models or you can build your own model from scratch using your own data and criteria.

Third, filter out samples by confidence so you eliminate those samples that are likely to lead to inaccurate predictions.

Finally, you should add a third step on the zap to save the results (for example, on a spreadsheet on Google Sheets or Excel) and create all kinds of data visualizations!

Sentiment Analysis in Google Sheets

Sentiment analysis with Google Sheets and MonkeyLearn’s add-on is pretty straightforward and simple. You can analyze the sentiment in almost every type of text by following 5 easy steps.

First, you must install MonkeyLearn’s add-on. To do so, go to Add-ons/Get add-ons, search for MonkeyLearn, and add it to your list.

Second, copy your MonkeyLearn’s API Token and paste it in the add-on Set token textbox: Go to Add-ons/MonkeyLearn and click Set token.

Third, start the add-on. Go to Add-ons/MonkeyLearn and click Start. A pop up will appear. You will be able to choose what model to use (e.g. Sentiment Analysis or Tweet Sentiment) and select the data you want to analyze.

Fourth, choose the data you want to analyze. Type the cell range that contains your texts into the Column or range textbox or select your data and choose Active Range to analyze it.

Finally, click Run and perform any kind of analysis or visualization you can think of.

On this step-by-step guide, we explain how to make the most out of our Google Sheets add-on to help you get started with sentiment analysis. We also explain some best practices and provide examples of interesting things you can do with your data.

Sentiment Analysis with RapidMiner

RapidMiner is a platform where you can create data mining processes without being an experienced data scientist. It provides a friendly user interface where you can create complete data analysis workflows, including loading your data, running machine learning models, and create visualizations. It’s simple to use and someone with no coding skills can quickly create automated processes and analyses of data.

Doing sentiment analysis with RapidMiner is pretty straight-forward with the MonkeyLearn extension.

First, you have to add the data (i.e. a source) from your computer to RapidMiner. You can upload data from a CSV file, a database, or use other data sources available on RapidMiner marketplace to import data from sources like Facebook, SAS, Tableau, and others.

As a second step, you have to add the MonkeyLearn classify operator and connect it to the input (your data). This operator allows using text classifiers available on MonkeyLearn including those trained specifically for sentiment analysis. During this step, you have to specify your MonkeyLearn API token, specify which sentiment analysis model you want to use (Module ID), and select the input attribute (this would be the text sent to MonkeyLearn to perform the sentiment analysis).

Finally, you have to connect the output of the MonkeyLearn classify operator to the results port, click on ‘run’ and voilà! You will get the results of running sentiment analysis on your data with zero lines of code!

Next Steps: Research Literature

So far, we’ve read about the basics of sentiment analysis, we’ve had a first-hand experience with a sentiment analysis model using an online demo, and we’ve gotten our hands dirty by experimenting with a tutorial in our domain.

By now, you are eager to level up your skills, want to learn more about sentiment analysis in detail, and experiment with more advanced stuff. In that case, a sound next step would be to dig into research and scientific literature.

Papers about Sentiment Analysis

The literature around sentiment analysis is massive; there are more than 55,700 scholarly articles, papers, theses, books, and abstracts out there.

The following are the most frequently cited and read papers in the sentiment analysis community in general:

Books about Sentiment Analysis

Bing Liu is an eminence in the field and has written a sound book that’s super useful for those starting research on sentiment analysis. Liu does a wonderful job explaining sentiment analysis in a way that is highly technical, yet understandable. Liu covers different aspects of sentiment analysis including applications, research, sentiment classification using supervised and unsupervised learning, sentence subjectivity, aspect-based sentiment analysis, and more.

Courses and Lectures

Another good way to go deeper with sentiment analysis is mastering your knowledge and skills in natural language processing (NLP), the computer science field that focuses on understanding ‘human’ language.

By combining machine learning, computational linguistics, and computer science, NLP allows a machine to understand natural language including people's sentiments, evaluations, attitudes, and emotions from written language.

There are a large number of courses, lectures, and resources available online, but the essential NLP course is the Stanford Coursera course by Dan Jurafsky and Christopher Manning. By taking this course, you will get a step-by-step introduction to the field by two of the most reputable names in the NLP community.

If you want a more hands-on course, you should enroll in the Data Science: Natural Language Processing (NLP) in Python on Udemy. This course gives you a good introduction to NLP and what it can do, but it will also make you build different projects in Python, including a spam detector, a sentiment analyzer, and an article spinner. Most of the lectures are really short (~5 minutes) and the course strikes the right balance between practical and theoretical content.

Sentiment Analysis Datasets

The key part for mastering sentiment analysis is working on different datasets and experiment different approaches. To do so, you first need to get your hands on data and procure a dataset over which you will do your experiments on based on your domain and interests.

The following are some of our favorite sentiment analysis datasets for experimenting with sentiment analysis and a machine learning approach. They’re open and free to download:

  • Product reviews: this dataset consists of a few million Amazon customer reviews with star ratings, super useful for training a sentiment analysis model.
  • Restaurant reviews: this dataset consists of 5,2 million Yelp reviews with star ratings.
  • Movie reviews: this dataset consists of 1,000 positive and 1,000 negative processed reviews. It also provides 5,331 positive and 5,331 negative processed sentences / snippets.
  • Fine food reviews: this dataset consists of ~500,000 food reviews from Amazon. It includes product and user information, ratings, and a plain text version of every review.
  • Twitter airline sentiment on Kaggle: this dataset consists of ~15,000 labeled tweets (positive, neutral, and negative) about airlines.
  • First GOP Debate Twitter Sentiment: this dataset consists of ~14,000 labeled tweets (positive, neutral, and negative) about the first GOP debate in 2016.

If you are interested in rule-based approach, the following is a varied list of sentiment analysis lexicons that will come in handy. These lexicons provide a set of dictionaries of words with labels specifying their sentiments across different domains. The following lexicons are really useful to identify the sentiment of texts:

Sentiment Analysis APIs

There are multiple options on Sentiment Analysis systems that can be consumed through an API. Broadly speaking, they can be classified into two different categories:

  • Open Source libraries
  • SaaS APIs

Open Source Libraries

Within open source libraries, there are programming languages such as Python or Java that are particularly well positioned since they have a strong data science community and, as a result, open source libraries for data science, including natural language processing. In all of these cases, you must have a strong knowledge of machine learning and programming in order to use the libraries successfully.

Sentiment Analysis APIs for Python

Python is one of the top programming languages for data science and it has a strong community and a large set of options to implement NLP models.

The following are remarkable examples:

Scikit-learn is the go-to library for Machine Learning and has useful tools for text vectorization. Training a classifier on top of vectorizations like frequency or tf-idf text vectorizers is very straightforward. Scikit-learn has implementations for Support Vector Machines, Naïve Bayes, and Logistic Regression, among others.

NLTK has been the traditional NLP library for Python. It has an active community and, besides providing low level functions for NLP, it also provides the possibility to train machine learning classifiers.

SpaCy is another recent NLP library with a growing community. Like NLTK, it provides a strong set of low-level functions for NLP and support for training text classifiers.

With the Deep Learning trend, in the last few years, a new set of data science libraries have been developed that have support for NLP applications. Some of the most remarkable:

TensorFlow. Developed by Google, it provides a low-level set of tools to build and train neural networks. There's also support for text vectorization, both on traditional word frequency and on more advanced through word embeddings.

Keras provides useful abstractions to work with multiple neural network types like recurrent neural networks (RNNs) and convolutional neural networks (CNNs) and easily stack layers of neurons. Keras can be run on top of Tensorflow or Theano. It also provides useful tools for text classification.

PyTorch is a recent Deep Learning framework backed by some prestigious organizations like Facebook, Twitter, Nvidia, Salesforce, Stanford University, University of Oxford, and Uber. It has quickly developed a strong community.

Sentiment Analysis APIs in Java

Java is another programming language with a strong community around data science with remarkable data science libraries for NLP.

  • OpenNLP: a toolkit that supports the most common NLP tasks, such as tokenization, sentence segmentation, part-of-speech tagging, named entity extraction, chunking, parsing, language detection and coreference resolution.
  • Stanford CoreNLP: a Java suite of core NLP tools provided by The Stanford NLP Group.
  • Lingpipe: a Java toolkit for processing text using computational linguistics. LingPipe is often used for text classification and entity extraction.
  • Weka: a set of tools created by The University of Waikato for data pre-processing, classification, regression, clustering, association rules, and visualization.

Sentiment Analysis SaaS APIs

Implementing a sentiment analysis system from scratch is not an easy task. Usually, companies need to spend a lot of time, money, and resources in the following:

Having a data science team. Having a development team. Deploying and scaling the infrastructure to train and run the models. Implementing and deploying an API to consume the models. Implementing tools to tag training examples. Adjusting the model hyperparameters.

If you want to avoid these hassles a great shortcut is to use sentiment analysis SaaS APIs which usually solve most of the problems mentioned above. Another important advantage of SaaS APIs is the possibility to easily use them from any system, that is, any programming language. There are lot of programming languages where software is built, but few of them have strong libraries for data science.

The following is a list of sentiment analysis SaaS APIs worth taking a look:

  • MonkeyLearn
  • Google Cloud NLP
  • IBM Watson
  • Amazon Comprehend
  • Lexalytics
  • Aylien
  • MeaningCloud
  • Rosette

Parting words

Sentiment analysis can be applied to countless aspects of business, from brand monitoring to product analytics, from customer service to market research. By incorporating it into their existing systems and analytics, leading brands (not to mention entire cities) are able to work faster, with more accuracy, toward more useful ends.

Sentiment analysis has moved beyond merely an interesting, high-tech whim, and will soon become an indispensable tool for all companies of the modern age. Ultimately, sentiment analysis enables us to glean new insights, better understand our customers, and empower our own teams more effectively so that they do better and more productive work.

MonkeyLearn is an online platform that makes it easy to analyze text with Machine Learning.

If you need help building a sentiment analysis system for your business, reach out and we’ll help you get started.