Sentiment Analysis: First Steps With Python’s NLTK Library

Sentiment Analysis Intro and Implementation by Farzad Mahmoodinobar

nlp for sentiment analysis

We will use the dataset which is available on Kaggle for sentiment analysis using NLP, which consists of a sentence and its respective sentiment as a target variable. This dataset contains 3 separate files named train.txt, test.txt and val.txt. This is why we need a process that makes the computers understand the Natural Language as we humans do, and this is what we call Natural Language Processing(NLP). And, as we know Sentiment Analysis is a sub-field of NLP and with the help of machine learning techniques, it tries to identify and extract the insights. Sentiment analysis and Semantic analysis are both natural language processing techniques, but they serve distinct purposes in understanding textual content.

nlp for sentiment analysis

This analysis can point you towards friction points much more accurately and in much more detail. It’s estimated that people only agree around 60-65% of the time when determining the sentiment of a particular text. Tagging text by sentiment is highly subjective, influenced by personal experiences, thoughts, and beliefs. Notice that the function removes all @ mentions, stop words, and converts the words to lowercase. The function lemmatize_sentence first gets the position tag of each token of a tweet.

If you know what consumers are thinking (positively or negatively), then you can use their feedback as fuel for improving your product or service offerings. One common type of NLP program uses artificial neural networks (computer programs) that are modeled after the neurons in the human brain; this is where the term “Artificial Intelligence” comes from. Once enough data has been gathered, these programs start getting good at figuring out if someone is feeling positive or negative about something just through analyzing text alone. However, while a computer can answer and respond to simple questions, recent innovations also let them learn and understand human emotions. A hybrid approach to text analysis combines both ML and rule-based capabilities to optimize accuracy and speed. While highly accurate, this approach requires more resources, such as time and technical capacity, than the other two.

You can analyze bodies of text, such as comments, tweets, and product reviews, to obtain insights from your audience. In this tutorial, you’ll learn the important features of NLTK for processing text data and the different approaches you can use to perform sentiment analysis on your data. For example, if a customer expresses a negative opinion along with a positive opinion in a review, a human assessing the review might label it negative before reaching the positive words. AI-enhanced sentiment classification helps sort and classify text in an objective manner, so this doesn’t happen, and both sentiments are reflected. To solve this problem, we will follow the typical machine learning pipeline.

And, because of this upgrade, when any company promotes their products on Facebook, they receive more specific reviews which will help them to enhance the customer experience. Semantic analysis, on the other hand, goes beyond sentiment and aims to comprehend the meaning and context of the text. It seeks to understand the relationships between words, phrases, and concepts in a given piece of content.

You will use the negative and positive tweets to train your model on sentiment analysis later in the tutorial. The .train() and .accuracy() methods should receive different portions of the same list of features. It involves using artificial neural networks, which are inspired by the structure of the human brain, to classify text into positive, negative, or neutral sentiments.

Suppose, there is a fast-food chain company and they sell a variety of different food items like burgers, pizza, sandwiches, milkshakes, etc. They have created a website to sell their food and now the customers can order any food item from their website and they can provide reviews as well, like whether they liked the food or hated it. In the play store, all the comments in the form of 1 to 5 are done with the help of sentiment analysis approaches.

If Chewy wanted to unpack the what and why behind their reviews, in order to further improve their services, they would need to analyze each and every negative review at a granular level. Maybe you want to track brand sentiment so you can detect disgruntled customers immediately and respond as soon as possible. Maybe you want to compare sentiment from one quarter to the next to see if you need to take action. Then you could dig deeper into your qualitative data to see why sentiment is falling or rising. One of the downsides of using lexicons is that people express emotions in different ways.

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Sentiment analysis helps businesses process huge amounts of unstructured data in an efficient and cost-effective way. Usually, when analyzing sentiments of texts you’ll want to know which particular aspects or features people are mentioning in a positive, neutral, or negative way. Accuracy is defined as the percentage of tweets in the testing dataset for which the model was correctly able to predict the sentiment. You will use the Naive Bayes classifier in NLTK to perform the modeling exercise. Notice that the model requires not just a list of words in a tweet, but a Python dictionary with words as keys and True as values.

First, you’ll use Tweepy, an easy-to-use Python library for getting tweets mentioning #NFTs using the Twitter API. Then, you will use a sentiment analysis model from the 🤗Hub to analyze these tweets. Finally, you will create some visualizations to explore the results and find some interesting insights. In this tutorial, you’ll use the IMDB dataset to fine-tune a DistilBERT model for sentiment analysis. Are you interested in doing sentiment analysis in languages such as Spanish, French, Italian or German? On the Hub, you will find many models fine-tuned for different use cases and ~28 languages.

nlp for sentiment analysis

Without normalization, “ran”, “runs”, and “running” would be treated as different words, even though you may want them to be treated as the same word. In this section, you explore stemming and lemmatization, which are two popular techniques of normalization. These return values indicate the number of times each word occurs exactly as given. Since all words in the stopwords list are lowercase, and those in the original list may not be, you use str.lower() to account for any discrepancies.

The emotion is then graded on a scale of zero to 100, similar to the way consumer websites deploy star-ratings to measure customer satisfaction. Sentiment analysis, or opinion mining, is the process of analyzing large volumes of text to determine whether it expresses a positive sentiment, a negative sentiment or a neutral sentiment. In the code above, we define that the max_features should be 2500, which means that it only uses the 2500 most frequently occurring words to create a “bag of words” feature vector. Words that occur less frequently are not very useful for classification. It is evident from the output that for almost all the airlines, the majority of the tweets are negative, followed by neutral and positive tweets.

Next, we remove all the single characters left as a result of removing the special character using the re.sub(r’\s+[a-zA-Z]\s+’, ‘ ‘, processed_feature) regular expression. For instance, if we remove the special character ‘ from Jack’s and replace it with space, we are left with Jack s. Here s has no meaning, so we remove it by replacing all single characters with a space. Sentiment analysis empowers all kinds of market research and competitive analysis.

Note also that you’re able to filter the list of file IDs by specifying categories. This categorization is a feature specific to this corpus and others of the same type. Different corpora have different features, so you may need to use Python’s help(), as in help(nltk.corpus.tweet_samples), or consult NLTK’s documentation to learn how to use a given corpus. One of them is .vocab(), which is worth mentioning because it creates a frequency distribution for a given text.

Selecting Useful Features

There are different algorithms you can implement in sentiment analysis models, depending on how much data you need to analyze, and how accurate you need your model to be. But with sentiment analysis tools, Chewy could plug in their 5,639 (at the time) TrustPilot reviews to gain instant sentiment analysis insights. In the world of machine learning, these data properties Chat PG are known as features, which you must reveal and select as you work with your data. While this tutorial won’t dive too deeply into feature selection and feature engineering, you’ll be able to see their effects on the accuracy of classifiers. A company launching a new line of organic skincare products needed to gauge consumer opinion before a major marketing campaign.

There are certain issues that might arise during the preprocessing of text. For instance, words without spaces (“iLoveYou”) will be treated as one and it can be difficult to separate such words. Furthermore, “Hi”, “Hii”, and “Hiiiii” will be treated differently by the script unless you write something specific to tackle the issue.

nlp for sentiment analysis

Get an understanding of customer feelings and opinions, beyond mere numbers and statistics. Understand how your brand image evolves over time, and compare it to that of your competition. You can tune into a specific point in time to follow product releases, marketing campaigns, IPO filings, etc., and compare them to past events. Not only do brands have a wealth of information available on social media, but across the internet, on news sites, blogs, forums, product reviews, and more. Again, we can look at not just the volume of mentions, but the individual and overall quality of those mentions. 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.

Monitoring sales is one way to know, but will only show stakeholders part of the picture. Using sentiment analysis on customer review sites and social media to identify the emotions being expressed about the product will enable a far deeper understanding of how it is landing with customers. SaaS tools offer the option to implement pre-trained sentiment analysis models immediately or custom-train your own, often in just a few steps. These tools are recommended if you don’t have a data science or engineering team on board, since they can be implemented with little or no code and can save months of work and money (upwards of $100,000).

Step 6 — Preparing Data for the Model

When training the model, you should provide a sample of your data that does not contain any bias. To avoid bias, you’ve added code to randomly arrange the data using the .shuffle() method of random. Sentiment analysis can be used to categorize text into a variety of sentiments. For simplicity and availability of the training dataset, this tutorial helps you train your model in only two categories, positive and negative.

You’ll begin by installing some prerequisites, including NLTK itself as well as specific resources you’ll need throughout this tutorial. Next, you will set up the credentials for interacting with the Twitter API. Then, you have to create a new project and connect an app to get an API key and token. We will evaluate our model using various metrics such as Accuracy Score, Precision Score, Recall Score, Confusion Matrix and create a roc curve to visualize how our model performed. And then, we can view all the models and their respective parameters, mean test score and rank as  GridSearchCV stores all the results in the cv_results_ attribute. Now, we will concatenate these two data frames, as we will be using cross-validation and we have a separate test dataset, so we don’t need a separate validation set of data.

  • We can even break these principal sentiments(positive and negative) into smaller sub sentiments such as “Happy”, “Love”, ”Surprise”, “Sad”, “Fear”, “Angry” etc. as per the needs or business requirement.
  • Yes, sentiment analysis is a subset of AI that analyzes text to determine emotional tone (positive, negative, neutral).
  • This code imports the WordNetLemmatizer class and initializes it to a variable, lemmatizer.
  • Chewy is a pet supplies company – an industry with no shortage of competition, so providing a superior customer experience (CX) to their customers can be a massive difference maker.

A large amount of data that is generated today is unstructured, which requires processing to generate insights. Some examples of unstructured data are news articles, posts on social media, and search history. The process of analyzing natural language and making sense out of it falls under the field of Natural Language Processing (NLP). Sentiment analysis is a common NLP task, which involves classifying texts or parts of texts into a pre-defined sentiment. You will use the Natural Language Toolkit (NLTK), a commonly used NLP library in Python, to analyze textual data.

A frequency distribution is essentially a table that tells you how many times each word appears within a given text. In NLTK, frequency distributions are a specific object type implemented as a distinct class called FreqDist. While you’ll use corpora provided by NLTK for this tutorial, it’s possible to build your own text corpora from any source. Building a corpus can be as simple as loading some plain text or as complex as labeling and categorizing each sentence. Refer to NLTK’s documentation for more information on how to work with corpus readers. NLTK provides a number of functions that you can call with few or no arguments that will help you meaningfully analyze text before you even touch its machine learning capabilities.

It’s an example of why it’s important to care, not only about if people are talking about your brand, but how they’re talking about it. If you are new to sentiment analysis, then you’ll quickly notice improvements. For typical use cases, such as ticket routing, brand monitoring, and VoC analysis, you’ll save a lot of time and money on tedious manual tasks. The nlp for sentiment analysis first response with an exclamation mark could be negative, right? The problem is there is no textual cue that will help a machine learn, or at least question that sentiment since yeah and sure often belong to positive or neutral texts. More recently, new feature extraction techniques have been applied based on word embeddings (also known as word vectors).

This indicates a promising market reception and encourages further investment in marketing efforts. It focuses on a particular aspect for instance if a person wants to check the feature of the cell phone then it checks the aspect such as the battery, screen, and camera quality then aspect based is used. This category can be designed as very positive, positive, neutral, negative, or very negative. If the rating is 5 then it is very positive, 2 then negative, and 3 then neutral.

Within the if statement, if the tag starts with NN, the token is assigned as a noun. Similarly, if the tag starts with VB, the token is assigned as a verb. To incorporate this into a function that normalizes a sentence, you should first generate the tags for each token in the text, and then lemmatize each word using the tag.

The following function makes a generator function to change the format of the cleaned data. From this data, you can see that emoticon entities form some of the most common parts of positive tweets. Before proceeding to the next step, make sure you comment out the last line of the script that prints the top ten tokens.

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. You can foun additiona information about ai customer service and artificial intelligence and NLP. 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.

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. Or start learning how to perform sentiment analysis using MonkeyLearn’s API and the pre-built sentiment analysis model, with just six lines of code. Then, train your own custom sentiment analysis model using MonkeyLearn’s easy-to-use UI. Sentiment analysis can be used on any kind of survey – quantitative and qualitative – and on customer support interactions, to understand the emotions and opinions of your customers.

Bing Liu is a thought leader in the field of machine learning and has written a book about sentiment analysis and opinion mining. Uncover trends just as they emerge, or follow long-term market leanings through analysis of formal market reports and business journals. We already looked at how we can use sentiment analysis in terms of the broader VoC, so now we’ll dial in on customer service teams. You can use it on incoming surveys and support tickets to detect customers who are ‘strongly negative’ and target them immediately to improve their service.

Otherwise, you may end up with mixedCase or capitalized stop words still in your list. This will tell NLTK to find and download each resource based on its identifier. We have created this notebook so you can use it through this tutorial in Google Colab. We will find the probability of the class using the predict_proba() method of Random Forest Classifier and then we will plot the roc curve.

They are generally irrelevant when processing language, unless a specific use case warrants their inclusion. Wordnet is a lexical database for the English language that helps the script determine the base word. You need the averaged_perceptron_tagger resource to determine the context of a word in a sentence. If you would like to use your own dataset, you can gather tweets from a specific time period, user, or hashtag by using the Twitter API. In the case of movie_reviews, each file corresponds to a single review.

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 of the videos, posted to Facebook, was shared more than 87,000 times and viewed 6.8 million times by 6pm on Monday, just 24 hours later.

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By using this tool, the Brazilian government was able to uncover the most urgent needs – a safer bus system, for instance – and improve them first. Still, sentiment analysis is worth the effort, even if your sentiment analysis predictions are wrong from time to time. By using MonkeyLearn’s sentiment analysis model, you can expect correct predictions about 70-80% of the time you submit your texts for classification.

In this tutorial, you will prepare a dataset of sample tweets from the NLTK package for NLP with different data cleaning methods. Once the dataset is ready for processing, you will train a model on pre-classified tweets and use the model to classify the sample tweets into negative and positives sentiments. Do you want to train a custom model for sentiment analysis with your own data? You can fine-tune a model using Trainer API to build on top of large language models and get state-of-the-art results.

You may define and customize your categories to meet your sentiment analysis needs depending on how you want to read consumer feedback and queries. Similarly, max_df specifies that only use those words that occur in a maximum of 80% of the documents. Words that occur in all documents are too common and are not very useful for classification. Similarly, min-df is set to 7 which shows that include words that occur in at least 7 documents. There are many sources of public sentiment e.g. public interviews, opinion polls, surveys, etc. However, with more and more people joining social media platforms, websites like Facebook and Twitter can be parsed for public sentiment.

The dataset that we are going to use for this article is freely available at this GitHub link. All rights are reserved, including those for text and data mining, AI training, and similar technologies. For all open access content, the Creative Commons licensing terms apply. Java is another programming language with a strong community around data science with remarkable data science libraries for NLP.

As we can see that our model performed very well in classifying the sentiments, with an Accuracy score, Precision and  Recall of approx 96%. And the roc curve and confusion matrix are great as well which means that our model is able to classify the labels accurately, with fewer chances of error. The potential applications of sentiment analysis are vast and continue to grow with advancements in AI and machine learning technologies.

Virgin America is probably the only airline where the ratio of the three sentiments is somewhat similar. Sentiment analysis can be applied to countless aspects of business, from brand monitoring and product analytics, to customer service and 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.

nlp for sentiment analysis

Duolingo, a popular language learning app, received a significant number of negative reviews on the Play Store citing app crashes and difficulty completing lessons. To understand the specific issues and improve customer service, Duolingo employed sentiment analysis on their Play Store reviews. Regardless of the level or extent of its training, software has a hard time correctly identifying irony and sarcasm in a body of text. This is because often when someone is being sarcastic or ironic it’s conveyed through their tone of voice or facial expression and there is no discernable difference in the words they’re using. By using sentiment analysis to conduct social media monitoring brands can better understand what is being said about them online and why.

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. 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). You’ll notice that these results are very different from TrustPilot’s overview (82% excellent, etc). This is because MonkeyLearn’s sentiment analysis AI performs advanced sentiment analysis, parsing through each review sentence by sentence, word by word.

Notice pos_tag() on lines 14 and 18, which tags words by their part of speech. NLTK offers a few built-in classifiers that are suitable for various types of analyses, including sentiment analysis. The trick is to figure out which properties of your dataset are useful in classifying each piece of data into your desired categories. The special thing about this corpus is that it’s already been classified. Therefore, you can use it to judge the accuracy of the algorithms you choose when rating similar texts.

Using pre-trained models publicly available on the Hub is a great way to get started right away with sentiment analysis. These models use deep learning architectures such as transformers that achieve state-of-the-art performance on sentiment analysis and other machine learning tasks. However, you can fine-tune a model with your own data to further improve the sentiment analysis results and get an extra boost of accuracy in your particular use case.

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But, for the sake of simplicity, we will merge these labels into two classes, i.e. We can view a sample of the contents of the dataset using the “sample” method of pandas, and check the no. of records and features using the “shape” method. We can even break these principal sentiments(positive and negative) into smaller sub sentiments such as “Happy”, “Love”, ”Surprise”, “Sad”, “Fear”, “Angry” etc. as per the needs or business requirement.

Rather than using polarities, like positive, negative or neutral, emotional detection can identify specific emotions in a body of text such as frustration, indifference, restlessness and shock. In this article, we saw how different Python libraries contribute to performing sentiment analysis. We performed an analysis of public tweets regarding six US airlines and achieved an accuracy of around 75%. I would recommend you to try and use some other machine learning algorithm such as logistic regression, SVM, or KNN and see if you can get better results. Statistical algorithms use mathematics to train machine learning models. To make statistical algorithms work with text, we first have to convert text to numbers.

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