5 Google Chrome Extensions Every Data Scientist Should Know About

Daniel Morales
Sep 17, 2021

Contents Outline

5 Google Chrome Extensions Every Data Scientist Should Know About

Sep 17, 2021 5 minutes read

In this new post we will talk about the best Google Chrome extensions that as data scientists make certain tasks easier for us. You should at least try them out and verify the results on your own, it is possible that they will become part of your arsenal of tools to work with on a daily basis. 

If you have any additional recommendations feel free to post them in the comments, or if you have any reviews on the mentioned extensions we would also like to hear from you!


#1- AI/ML Papers with Code Everywhere - CatalyzeX





Extension description:

💻 Get the implementation code of machine learning research papers with code directly on Google, ArXiv, Scholar, Twitter, Github, etc.
CatalyzeX free browser extension instantly finds and displays the implementation code of any machine learning, artificial intelligence, natural language processing, computer vision, reinforcement learning, and deep learning research papers with code you find while browsing Google, ArXiv, Twitter, Scholar, Github, and other websites.

▶ Browse the web as usual and you'll start seeing [CODE] buttons next to documents everywhere.
▶ The [CODE] buttons will automatically appear directly on the page of any implementation link found.
▶ Click any code button to instantly jump to open source and explore!

Powered by the CatalyzeX.com repository used by thousands of engineers, researchers, developers and technology leaders from around the world - to browse ML algorithms, models and articles with code for relevant and cutting-edge developments in machine learning, data science, artificial intelligence, computer vision, natural language processing, speech recognition, reinforcement learning and deep learning.

Download link: https://chrome.google.com/webstore/detail/aiml-papers-with-code-eve/aikkeehnlfpamidigaffhfmgbkdeheil

#2- Instant Data Scraper



Extension description:

Instant Data Scraper extracts data from web pages and exports it as Excel or CSV files.
Instant Data Scraper is an automated data extraction tool for any website. It uses AI to predict what data is most relevant on an HTML page and allows you to save it to an Excel or CSV file (XLS, XLSX, CSV).

This tool does not require website-specific scripts, but uses AI heuristic analysis of the HTML structure to detect the data to extract. If the prediction is not satisfactory, it allows the user to customize the selections for greater accuracy. This type of scrape technology is much more convenient, because it does not require large libraries of user-created scrape scripts, which are often filled with obsolete and redundant versions. This means that our scrape method works just as well with small, lesser-known websites as it does with global giants like Amazon. Plus, our users don't need to have any coding, json or xml knowledge!

Instant Data Scraper features:
* Data detection for extraction with AI.
* Detection of dynamic data when it has been loaded.
* Customization of delay and timeout for desired crawl speed.
* Support for pagination on web sites.
* Automatic navigation to the next page via buttons or links.
* Support for infinite scroll.
* Preview of extracted data with copy and paste support.
* Data export to Excel spreadsheet or CSV file.
* Rename and filter extracted data columns.

This extension is completely FREE. Instant Data Scraper works well in unison with SEO tools, CRM recruiting systems, sales lead management tools or email marketing campaigns. Web scraping and data downloading is made easy with our tool. Plus, you have data security and privacy as scraped data does not leave your browser.

Instant Data Scraper USE CASES:
* Lead generation for companies and freelancers.
* Growth hackers looking for easy ways to collect data.
* Recruiters looking for job candidates.
* Obtaining search engine results.
* Obtaining product pricing data from e-commerce websites.
* Amazon sellers, distributors and review analysts.
* Obtain email and directory addresses and phone numbers.
* Get contact information from professional association websites.
* Collect reviews and ratings.
* Analyze posts for likes, comments, connection and contacts.
* Extract emails and IDs from social network profiles.
Developer's promise: This extension does not contain any malware or spyware beyond the standard Google Analytics.

Download link: https://chrome.google.com/webstore/detail/instant-data-scraper/ofaokhiedipichpaobibbnahnkdoiiah


#3- EquatIO - Math made digital



Extension description:

Easily create mathematical equations, formulas and quizzes. Type intuitively or by hand, without the need to learn complicated mathematical code.

Until now, writing mathematical equations and expressions on the computer was slow and laborious.

EquatIO makes mathematics digital, helping teachers and students of all levels to create mathematical expressions quickly and easily.

Type or handwrite virtually any mathematical expression directly on your keyboard or touch screen. There is no need for any complicated code or programming languages.

EquatIO instantly converts your thoughts into clear and precise formulas on the screen. When you type "sq", it knows you mean "square root". And it listens to you, too. When you dictate a formula out loud, EquatIO is smart enough to ignore "umms," "errs," and other unwanted non-math words.

More than a substitute for pencil and paper, EquatIO makes math and other STEM subjects engaging and rewarding for all students.

Features:
- Easily create mathematical expressions, including equations and formulas.
- Compatible with Google Docs, Forms*, Slides*, Sheets* and Drawings*.
- Keyboard input, handwriting recognition* (via touchscreen or touchpad), and voice dictation
- Guess what you're writing or typing, just like predictive text on your smartphone*.
- Hear your mathematical expressions read aloud.
- Compatible with LaTeX input for advanced users.
- Create interactive digital math quizzes*.
- Enter student responses directly into digital quizzes*.
- Chemistry formula prediction*.


Download link: https://chrome.google.com/webstore/detail/equatio-math-made-digital/hjngolefdpdnooamgdldlkjgmdcmcjnc


4- Challenge Hunt



Extension description:

One application. All programming competitions. Keeps you up to date with all active and upcoming programming competitions and hackathons from around the world.
Challenge Hunt brings you the best programming challenges from around the world. Keeps you up to date with all active and upcoming coding competitions, hackathons, hiring and data science challenges. It allows you to:

1. see all active and upcoming:
* Coding competitions
* Hackathons
* Data science challenges
* Hiring challenges

2. Set reminders about upcoming challenges so you don't miss any challenges.

3. Set your preferred online challenge platforms and Challenge Hunt will show you challenges only from those platforms.

Download link: https://chrome.google.com/webstore/detail/challenge-hunt/cgbnhngdlmhjbmgkekedepoapmoingjj


5- Open in Colab



Extension description:

Open a notebook hosted on Github in Google Colab. Simple browser extension to quickly open Jupyter notebook hosted on GitHub in Google Colab.

Download link: https://chrome.google.com/webstore/detail/open-in-colab/iogfkhleblhcpcekbiedikdehleodpjo

Thanks for reading us!

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10 Highly Probable Data Scientist Interview Questions

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However, I suggest reading or studying each one in more detail afterwards.Machine Learning1. What is overfitting?Overfitting in machine learning occurs when your model is not generalized well. The model is too focused on the training set. It captures a lot of detail or even noise in the training set. Thus, it fails to capture the general trend or the relationships in the data. If a model is too complex compared to the data, it will probably be overfitting.A strong indicator of overfitting is the high difference between the accuracy of training and test sets. Overfit models usually have very high accuracy on the training set but the test accuracy is usually unpredictable and much lower than the training accuracy.2. How can you reduce overfitting?We can reduce overfitting by making the model more generalized which means it should be more focused on the general trend rather than specific details.If it is possible, collecting more data is an efficient way to reduce overfitting. You will be giving more juice to the model so it will have more material to learn from. Data is always valuable especially for machine learning models.Another method to reduce overfitting is to reduce the complexity of the model. If a model is too complex for a given task, it will likely result in overfitting. In such cases, we should look for simpler models.3. What is regularization?We have mentioned that the main reason for overfitting is a model being more complex than necessary. Regularization is a method for reducing the model complexity.It does so by penalizing higher terms in the model. With the addition of a regularization term, the model tries to minimize both loss and complexity.Two main types of regularization are L1 and L2 regularization. L1 regularization subtracts a small amount from the weights of uninformative features at each iteration. Thus, it causes these weights to eventually become zero.On the other hand, L2 regularization removes a small percentage from the weights at each iteration. These weights will get closer to zero but never actually become 0.4. What is the difference between classification and clustering?Both are machine learning tasks. Classification is a supervised learning task so we have labelled observations (i.e. data points). We train a model with labelled data and expect it to predict the labels of new data.For instance, spam email detection is a classification task. We provide a model with several emails marked as spam or not spam. After the model is trained with those emails, it will evaluate the new emails appropriately.Clustering is an unsupervised learning task so the observations do not have any labels. The model is expected to evaluate the observations and group them into clusters. Similar observations are placed into the same cluster.In the optimal case, the observations in the same cluster are as close to each other as possible and the different clusters are as far apart as possible. An example of a clustering task would be grouping customers based on their shopping behavior.PythonThe built-in data structures are of crucial importance. Thus, you should be familiar with what they are and how to interact with them. List, dictionary, set, and tuple are 4 main built-in data structures in Python.5. What is the difference between lists and tuplesThe main difference between lists and tuples is mutability. Lists are mutable so we can manipulate them by adding or removing items.mylist = [1,2,3] mylist.append(4) mylist.remove(1) print(mylist) [2,3,4]On the other hand, tuples are immutable. Although we can access each element in a tuple, we cannot modify its content.mytuple = (1,2,3) mytuple.append(4) AttributeError: 'tuple' object has no attribute 'append'One important point to mention here is that although tuples are immutable, they can contain mutable elements such as lists or sets.mytuple = (1,2,["a","b","c"]) mytuple[2] ['a', 'b', 'c'] mytuple[2][0] = ["A"] print(mytuple) (1, 2, [['A'], 'b', 'c'])6. What is the difference between lists and setsLet’s do an example to demonstrate the main difference between lists and sets.text = "Python is awesome!" mylist = list(text) myset = set(text) print(mylist) ['P', 'y', 't', 'h', 'o', 'n', ' ', 'i', 's', ' ', 'a', 'w', 'e', 's', 'o', 'm', 'e', '!'] print(myset) {'t', ' ', 'i', 'e', 'm', 'P', '!', 'y', 'o', 'h', 'n', 'a', 's', 'w'}As we notice in the resulting objects, the list contains all the characters in the string whereas the set only contains unique values.Another difference is that the characters in the list are ordered based on their location in the string. However, there is no order associated with the characters in the set.Here is a table that summarizes the main characteristics of lists, tuples, and sets.(image by author)7. What is a dictionary and what are the important features of dictionaries?A dictionary in Python is a collection of key-value pairs. It is similar to a list in the sense that each item in a list has an associated index starting from 0.mylist = ["a", "b", "c"] mylist[1] "b"In a dictionary, we have keys as the index. Thus, we can access a value by using its key.mydict = {"John": 24, "Jane": 26, "Ashley": 22} mydict["Jane"] 26The keys in a dictionary are unique which makes sense because they act like an address for the values.SQLSQL is an extremely important skill for data scientists. There are quite a number of companies that store their data in a relational database. SQL is what is needed to interact with relational databases.You will probably be asked a question that involves writing a query to perform a specific task. You might also be asked a question about general database knowledge.8. Query example 1Consider we have a sales table that contains daily sales quantities of products.SELECT TOP 10 * FROM SalesTable(image by author)Find the top 5 weeks in terms of total weekly sales quantities.SELECT TOP 5 CONCAT(YEAR(SalesDate), DATEPART(WEEK, SalesDate)) AS YearWeek, SUM(SalesQty) AS TotalWeeklySales FROM SalesTable GROUP BY CONCAT(YEAR(SalesDate), DATEPART(WEEK, SalesDate)) ORDER BY TotalWeeklySales DESC (image by author)We first extract the year and week information from the date column and then use it in the aggregation. The sum function is used to calculate the total sales quantities.9. Query example 2In the same sales table, find the number of unique items that are sold each month.SELECT MONTH(SalesDate) AS Month, COUNT(DISTINCT(ItemNumber)) AS ItemCount FROM SalesTable GROUP BY MONTH(SalesDate) Month ItemCount 1 9 1021 2 8 102110. What is normalization and denormalization in a database?These terms are related to database schema design. 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Data Science
Machine Learning
11 Kaggle Alternatives in Data Science Competitions

Data science competitions are a very particular field of applied machine learning, or what is commonly known as applied AI. From the point of view of a data scientist, it has the particularity of simulating a real environment for the solution of a machine learning problem. From the point of view of a company, it has the particularity of solving a problem in a collaborative way (following the wisdom of crowds) and obtaining the benefits derived from it: such as benchmarking, new ideas, different solutions. As we mentioned in a previous blog post about data science competitions, some time ago several platforms were born among which is Kaggle and in which large technology companies in Silicon Valley and even Multinationals try to solve really complex problems with the help of outsiders, through something called "data science competitions". This was because internal talent could not solve these problems, because they did not have the time, resources or capabilities. 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That is why we have dedicated this blog post to show other options for sponsoring data science competitions.1- DataSource.aiCompany Targets: Startups & SMBsType Competitions: Cash PrizesCompetition System: Usually last 2-3 months each competitionAverage Opened Competitions per Month: 1Average Prize Money: Starting at USD $3.000Link: https://www.datasource.ai/The focus of this platform is to democratize data science competitions. Other data science competition platforms are focused on very large companies, very high prizes and very complex problems. This translates into competitions that can only be paid for by companies with deep pockets, competitions that take months to complete, and that are made for data scientists and "super-senior" teams. At the end of the day sponsoring a $20,000 USD (or 1 million USD) competition is not for every type of company. So they decided to rethink the way data science competitions are built and decided to focus on startups of any size and from any part of the world, that can afford competitions that are in line with a startup budget, that don't take so long to be solved (8 weeks), that can launch more than one, two or three competitions (because they can afford it) and in which all kinds of data science talent can participate, from any level and from any part of the world. 2- NumeraiCompany Targets: Finance, CryptoType Competitions: Crypto PrizesCompetition System: ContinuousAverage Opened Competitions per Month: ContinuousLink: https://numer.ai/In the Numerai Tournament you build machine learning models on abstract financial data to predict the stock market. Your models can be wagered with the NMR cryptocurrency to earn performance-based rewards. Numerai's wagered models combine to form the Meta Model which controls Numerai's hedge fund capital in the global stock market. Here companies are not allowed to sponsor competitions, Numerai is the sponsor itself and is the one who delivers the rewards3- International Data Analysis Olympiad (IDAHO)Company Targets: Made by Yandex onlyType Competitions: Money Prize and InternshipsCompetition System: Usually last 1 year each competitionAverage Opened Competitions per Year: 1Average Prize Money: $10.000Link: https://idao.world/IDAHO is an annual competition organized by the Higher School of Economics and Yandex. This event is open to all teams and individuals, be they undergraduate, postgraduate or Ph.D. students, company employees, researchers or new data scientists.4- DrivenDataCompany Targets: Social CompaniesType Competitions: Money Prize and KudosCompetition System: Usually last 2-4 months each competitionAverage Opened Competitions per Month: 2Average Prize Money: $17.000Link: https://www.drivendata.org/competitions/DrivenData brings cutting-edge practices in data science and crowdsourcing to some of the world’s biggest social challenges and the organizations taking them on5- CodaLabCompany Targets: Social and Big CompaniesType Competitions: KnowledgeCompetition System: Usually last 3-6 months each competitionAverage Opened Competitions per Month: 1Average Prize Money: Almost all are for knowledge Link: https://competitions.codalab.org/Codalab open-source platform for computational research. The competitions are held for the sake of collaborative research and code testing.6- DataHack & DSATCompany Targets: Social and Big CompaniesType Competitions: KudosCompetition System: Usually last 2-4 months each competitionAverage Opened Competitions per Month: 1Average Prize Money: All are hackathons without a final prize Link: https://datahack.analyticsvidhya.com/This platform basically allows you to compete with the best in the world on real-life data science problems, learn by working on real-world problems, showcase your expertise and get hired in top firms, build your profile, and be on the top of competitions and win lucrative prizes7- Machine HackCompany Targets: Social and Big CompaniesType Competitions: Money Prize and Kudos, InterviewsCompetition System: Usually last 2-4 months each competitionAverage Opened Competitions per Month: 1Average Prize Money: All are hackathons without a final prize Link: https://machinehack.com/Machine Hack is an online platform for Machine Learning competitions. At Machine Hack, you get to test and practice your ML skills. In this platform, you have the opportunity to compete against hundreds of Data Scientists, with our industry curated Hackathons. 8- TianchiCompany Targets: Big CompaniesType Competitions: Money Prize and KudosCompetition System: Usually last 3-6 months each competitionAverage Opened Competitions per Month: 1Average Prize Money: $100.000Link: https://tianchi.aliyun.com/competition/gameList/activeListTianchi is a crowdsourcing community of global data scientists that hosts big data competitions in various industries. This Big Data Competition has million-dollar prize pools and real business test cases. You have the chance to compete against AI elites from around the world.9- KDD CupCompany Targets: Organized by ACM Special Interest GroupType Competitions: Money PrizeCompetition System: Usually last 1 year each competitionAverage Opened Competitions per Month: 1Average Prize Money: $12.000Link: https://www.kdd.org/kdd-cupIs the annual Data Mining and Knowledge Discovery competition organized by ACM Special Interest Group on Knowledge Discovery and Data Mining, the leading professional organization of data miners. Year to year archives including datasets, instructions, and winners are available for most years10- vizdoomCompany Targets: Organized by VIZDOOMType Competitions: Money PrizeCompetition System: Usually last 1 year each competitionAverage Opened Competitions per Month: 1Average Prize Money: No applyLink: http://vizdoom.cs.put.edu.pl/competitions/vdaic-2017-cigVIZDOOM allows developing AI bots that play DOOM using the visual information (the screen buffer).11- Crowd AnalytiXCompany Targets: Medium Size CompaniesType Competitions: Money Prize and KudosCompetition System: Usually last 2-4 months each competitionAverage Opened Competitions per Month: 1Average Prize Money: $7.000Link: https://www.crowdanalytix.com/communityData experts collaborate & compete to build & optimize AI, ML, NLP and Deep Learning algorithmsConclusionIf you are a data scientist, you will definitely have a lot of learning and participation options. But make sure you also have a real chance to win!If you are a company and you are thinking about solving a data science problem, don't hesitate to make the decision for the best!

Data Science
Machine Learning
Model Evaluation Metrics in Machine Learning

CreditsPredictive models have become a trusted advisor to many businesses and for a good reason. These models can “foresee the future”, and there are many different methods available, meaning any industry can find one that fits their particular challenges.When we talk about predictive models, we are talking either about a regression model (continuous output) or a classification model (nominal or binary output). In classification problems, we use two types of algorithms (dependent on the kind of output it creates):Class output: Algorithms like SVM and KNN create a class output. For instance, in a binary classification problem, the outputs will be either 0 or 1. However, today we have algorithms that can convert these class outputs to probability.Probability output: Algorithms like Logistic Regression, Random Forest, Gradient Boosting, Adaboost, etc. give probability outputs. Converting probability outputs to class output is just a matter of creating a threshold probability.IntroductionWhile data preparation and training a machine learning model is a key step in the machine learning pipeline, it’s equally important to measure the performance of this trained model. How well the model generalizes on the unseen data is what defines adaptive vs non-adaptive machine learning models.By using different metrics for performance evaluation, we should be in a position to improve the overall predictive power of our model before we roll it out for production on unseen data.Without doing a proper evaluation of the ML model using different metrics, and depending only on accuracy, it can lead to a problem when the respective model is deployed on unseen data and can result in poor predictions.This happens because, in cases like these, our models don’t learn but instead memorize;hence, they cannot generalize well on unseen data.Model Evaluation MetricsLet us now define the evaluation metrics for evaluating the performance of a machine learning model, which is an integral component of any data science project. It aims to estimate the generalization accuracy of a model on the future (unseen/out-of-sample) data.Confusion MatrixA confusion matrix is a matrix representation of the prediction results of any binary testing that is often used to describe the performance of the classification model (or “classifier”) on a set of test data for which the true values are known.The confusion matrix itself is relatively simple to understand, but the related terminology can be confusing.Confusion matrix with 2 class labels.Each prediction can be one of the four outcomes, based on how it matches up to the actual value:True Positive (TP): Predicted True and True in reality.True Negative (TN): Predicted False and False in reality.False Positive (FP): Predicted True and False in reality.False Negative (FN): Predicted False and True in reality.Now let us understand this concept using hypothesis testing.A Hypothesis is speculation or theory based on insufficient evidence that lends itself to further testing and experimentation. With further testing, a hypothesis can usually be proven true or false.A Null Hypothesis is a hypothesis that says there is no statistical significance between the two variables in the hypothesis. It is the hypothesis that the researcher is trying to disprove.We would always reject the null hypothesis when it is false, and we would accept the null hypothesis when it is indeed true.Even though hypothesis tests are meant to be reliable, there are two types of errors that can occur.These errors are known as Type 1 and Type II errors.For example, when examining the effectiveness of a drug, the null hypothesis would be that the drug does not affect a disease.Type I Error:- equivalent to False Positives(FP).The first kind of error that is possible involves the rejection of a null hypothesis that is true.Let’s go back to the example of a drug being used to treat a disease. If we reject the null hypothesis in this situation, then we claim that the drug does have some effect on a disease. But if the null hypothesis is true, then, in reality, the drug does not combat the disease at all. The drug is falsely claimed to have a positive effect on a disease.Type II Error:- equivalent to False Negatives(FN).The other kind of error that occurs when we accept a false null hypothesis. This sort of error is called a type II error and is also referred to as an error of the second kind.If we think back again to the scenario in which we are testing a drug, what would a type II error look like? A type II error would occur if we accepted that the drug hs no effect on disease, but in reality, it did.A sample python implementation of the Confusion matrix.import warnings import pandas as pd from sklearn import model_selection from sklearn.linear_model import LogisticRegression from sklearn.metrics import confusion_matrix import matplotlib.pyplot as plt %matplotlib inline   #ignore warnings warnings.filterwarnings('ignore') # Load digits dataset url = "http://archive.ics.uci.edu/ml/machine-learning-databases/iris/iris.data" df = pd.read_csv(url) # df = df.values X = df.iloc[:,0:4] y = df.iloc[:,4] #test size test_size = 0.33 #generate the same set of random numbers seed = 7 #Split data into train and test set. X_train, X_test, y_train, y_test = model_selection.train_test_split(X, y, test_size=test_size, random_state=seed) #Train Model model = LogisticRegression() model.fit(X_train, y_train) pred = model.predict(X_test)  #Construct the Confusion Matrix labels = ['Iris-setosa', 'Iris-versicolor', 'Iris-virginica'] cm = confusion_matrix(y_test, pred, labels) print(cm) fig = plt.figure() ax = fig.add_subplot(111) cax = ax.matshow(cm) plt.title('Confusion matrix') fig.colorbar(cax) ax.set_xticklabels([''] + labels) ax.set_yticklabels([''] + labels) plt.xlabel('Predicted Values') plt.ylabel('Actual Values') plt.show()Confusion matrix with 3 class labels.The diagonal elements represent the number of points for which the predicted label is equal to the true label, while anything off the diagonal was mislabeled by the classifier. Therefore, the higher the diagonal values of the confusion matrix the better, indicating many correct predictions.In our case, the classifier predicted all the 13 setosa and 18 virginica plants in the test data perfectly. However, it incorrectly classified 4 of the versicolor plants as virginica.There is also a list of rates that are often computed from a confusion matrix for a binary classifier:1. AccuracyOverall, how often is the classifier correct?Accuracy = (TP+TN)/totalWhen our classes are roughly equal in size, we can use accuracy, which will give us correctly classified values.Accuracy is a common evaluation metric for classification problems. It’s the number of correct predictions made as a ratio of all predictions made.Misclassification Rate(Error Rate): Overall, how often is it wrong. Since accuracy is the percent we correctly classified (success rate), it follows that our error rate (the percentage we got wrong) can be calculated as follows:Misclassification Rate = (FP+FN)/totalWe use the sklearn module to compute the accuracy of a classification task, as shown below.#import modules import warnings import pandas as pd import numpy as np from sklearn import model_selection from sklearn.linear_model import LogisticRegression from sklearn import datasets from sklearn.metrics import accuracy_score #ignore warnings warnings.filterwarnings('ignore') # Load digits dataset iris = datasets.load_iris() # # Create feature matrix X = iris.data # Create target vector y = iris.target #test size test_size = 0.33 #generate the same set of random numbers seed = 7 #cross-validation settings kfold = model_selection.KFold(n_splits=10, random_state=seed) #Model instance model = LogisticRegression() #Evaluate model performance scoring = 'accuracy' results = model_selection.cross_val_score(model, X, y, cv=kfold, scoring=scoring) print('Accuracy -val set: %.2f%% (%.2f)' % (results.mean()*100, results.std()))  #split data X_train, X_test, y_train, y_test = model_selection.train_test_split(X, y, test_size=test_size, random_state=seed) #fit model model.fit(X_train, y_train) #accuracy on test set result = model.score(X_test, y_test) print("Accuracy - test set: %.2f%%" % (result*100.0))The classification accuracy is 88% on the validation set.2. PrecisionWhen it predicts yes, how often is it correct?Precision=TP/predicted yesWhen we have a class imbalance, accuracy can become an unreliable metric for measuring our performance. For instance, if we had a 99/1 split between two classes, A and B, where the rare event, B, is our positive class, we could build a model that was 99% accurate by just saying everything belonged to class A. Clearly, we shouldn’t bother building a model if it doesn’t do anything to identify class B; thus, we need different metrics that will discourage this behavior. For this, we use precision and recall instead of accuracy.3. Recall or SensitivityWhen it’s actually yes, how often does it predict yes?True Positive Rate = TP/actual yesRecall gives us the true positive rate (TPR), which is the ratio of true positives to everything positive.In the case of the 99/1 split between classes A and B, the model that classifies everything as A would have a recall of 0% for the positive class, B (precision would be undefined — 0/0). Precision and recall provide a better way of evaluating model performance in the face of a class imbalance. They will correctly tell us that the model has little value for our use case.Just like accuracy, both precision and recall are easy to compute and understand but require thresholds. Besides, precision and recall only consider half of the confusion matrix:4. F1 ScoreThe F1 score is the harmonic mean of the precision and recall, where an F1 score reaches its best value at 1 (perfect precision and recall) and worst at 0.Why harmonic mean? Since the harmonic mean of a list of numbers skews strongly toward the least elements of the list, it tends (compared to the arithmetic mean) to mitigate the impact of large outliers and aggravate the impact of small ones.An F1 score punishes extreme values more. Ideally, an F1 Score could be an effective evaluation metric in the following classification scenarios:When FP and FN are equally costly — meaning they miss on true positives or find false positives — both impact the model almost the same way, as in our cancer detection classification exampleAdding more data doesn’t effectively change the outcome effectivelyTN is high (like with flood predictions, cancer predictions, etc.)A sample python implementation of the F1 score.import warnings import pandas from sklearn import model_selection from sklearn.linear_model import LogisticRegression from sklearn.metrics import log_loss from sklearn.metrics import precision_recall_fscore_support as score, precision_score, recall_score, f1_score  warnings.filterwarnings('ignore')  url = "https://raw.githubusercontent.com/jbrownlee/Datasets/master/pima-indians-diabetes.data.csv" dataframe = pandas.read_csv(url) dat = dataframe.values X = dat[:,:-1] y = dat[:,-1] test_size = 0.33 seed = 7  model = LogisticRegression() #split data X_train, X_test, y_train, y_test = model_selection.train_test_split(X, y, test_size=test_size, random_state=seed) model.fit(X_train, y_train) precision = precision_score(y_test, pred) print('Precision: %f' % precision) # recall: tp / (tp + fn) recall = recall_score(y_test, pred) print('Recall: %f' % recall) # f1: tp / (tp + fp + fn) f1 = f1_score(y_test, pred) print('F1 score: %f' % f1)5. SpecificityWhen it’s no, how often does it predict no?True Negative Rate=TN/actual noIt is the true negative rate or the proportion of true negatives to everything that should have been classified as negative.Note that, together, specificity and sensitivity consider the full confusion matrix:6. Receiver Operating Characteristics (ROC) CurveMeasuring the area under the ROC curve is also a very useful method for evaluating a model. By plotting the true positive rate (sensitivity) versus the false-positive rate (1 — specificity), we get the Receiver Operating Characteristic (ROC) curve. This curve allows us to visualize the trade-off between the true positive rate and the false positive rate.The following are examples of good ROC curves. The dashed line would be random guessing (no predictive value) and is used as a baseline; anything below that is considered worse than guessing. We want to be toward the top-left corner:A sample python implementation of the ROC curves.#Classification Area under curve import warnings import pandas from sklearn import model_selection from sklearn.linear_model import LogisticRegression from sklearn.metrics import roc_auc_score, roc_curve  warnings.filterwarnings('ignore')  url = "https://raw.githubusercontent.com/jbrownlee/Datasets/master/pima-indians-diabetes.data.csv" dataframe = pandas.read_csv(url) dat = dataframe.values X = dat[:,:-1] y = dat[:,-1] seed = 7 #split data X_train, X_test, y_train, y_test = model_selection.train_test_split(X, y, test_size=test_size, random_state=seed) model.fit(X_train, y_train)  # predict probabilities probs = model.predict_proba(X_test) # keep probabilities for the positive outcome only probs = probs[:, 1]  auc = roc_auc_score(y_test, probs) print('AUC - Test Set: %.2f%%' % (auc*100))  # calculate roc curve fpr, tpr, thresholds = roc_curve(y_test, probs) # plot no skill plt.plot([0, 1], [0, 1], linestyle='--') # plot the roc curve for the model plt.plot(fpr, tpr, marker='.') plt.xlabel('False positive rate') plt.ylabel('Sensitivity/ Recall') # show the plot plt.show()In the example above, the AUC is relatively close to 1 and greater than 0.5. A perfect classifier will have the ROC curve go along the Y-axis and then along the X-axisLog LossLog Loss is the most important classification metric based on probabilities.As the predicted probability of the true class gets closer to zero, the loss increases exponentially:It measures the performance of a classification model where the prediction input is a probability value between 0 and 1. Log loss increases as the predicted probability diverge from the actual label. The goal of any machine learning model is to minimize this value. As such, smaller log loss is better, with a perfect model having a log loss of 0.A sample python implementation of the Log Loss.#Classification LogLoss import warnings import pandas from sklearn import model_selection from sklearn.linear_model import LogisticRegression from sklearn.metrics import log_loss  warnings.filterwarnings('ignore') url = "https://raw.githubusercontent.com/jbrownlee/Datasets/master/pima-indians-diabetes.data.csv" dataframe = pandas.read_csv(url) dat = dataframe.values X = dat[:,:-1] y = dat[:,-1] seed = 7 #split data X_train, X_test, y_train, y_test = model_selection.train_test_split(X, y, test_size=test_size, random_state=seed) model.fit(X_train, y_train) #predict and compute logloss pred = model.predict(X_test) accuracy = log_loss(y_test, pred) print("Logloss: %.2f" % (accuracy))Logloss: 8.02 Jaccard IndexJaccard Index is one of the simplest ways to calculate and find out the accuracy of a classification ML model. Let’s understand it with an example. Suppose we have a labeled test set, with labels as –y = [0,0,0,0,0,1,1,1,1,1]And our model has predicted the labels as –y1 = [1,1,0,0,0,1,1,1,1,1]The above Venn diagram shows us the labels of the test set and the labels of the predictions, and their intersection and union.Jaccard Index or Jaccard similarity coefficient is a statistic used in understanding the similarities between sample sets. The measurement emphasizes the similarity between finite sample sets and is formally defined as the size of the intersection divided by the size of the union of the two labeled sets, with formula as –Jaccard Index or Intersection over Union(IoU)So, for our example, we can see that the intersection of the two sets is equal to 8 (since eight values are predicted correctly) and the union is 10 + 10–8 = 12. So, the Jaccard index gives us the accuracy as –So, the accuracy of our model, according to Jaccard Index, becomes 0.66, or 66%.Higher the Jaccard index higher the accuracy of the classifier.A sample python implementation of the Jaccard index.import numpy as np def compute_jaccard_similarity_score(x, y):     intersection_cardinality = len(set(x).intersection(set(y)))     union_cardinality = len(set(x).union(set(y)))     return intersection_cardinality / float(union_cardinality)  score = compute_jaccard_similarity_score(np.array([0, 1, 2, 5, 6]), np.array([0, 2, 3, 5, 7, 9])) print "Jaccard Similarity Score : %s" %score passJaccard Similarity Score : 0.375Kolomogorov Smirnov chartK-S or Kolmogorov-Smirnov chart measures the performance of classification models. More accurately, K-S is a measure of the degree of separation between positive and negative distributions.The cumulative frequency for the observed and hypothesized distributions is plotted against the ordered frequencies. The vertical double arrow indicates the maximal vertical difference.The K-S is 100 if the scores partition the population into two separate groups in which one group contains all the positives and the other all the negatives. On the other hand, If the model cannot differentiate between positives and negatives, then it is as if the model selects cases randomly from the population. The K-S would be 0.In most classification models the K-S will fall between 0 and 100, and that the higher the value the better the model is at separating the positive from negative cases.The K-S may also be used to test whether two underlying one-dimensional probability distributions differ. It is a very efficient way to determine if two samples are significantly different from each other.A sample python implementation of the Kolmogorov-Smirnov.from scipy.stats import kstest import random   # N = int(input("Enter number of random numbers: ")) N = 10   actual =[] print("Enter outcomes: ")   for i in range(N):     # x = float(input("Outcomes of class "+str(i + 1)+": "))     actual.append(random.random())   print(actual) x = kstest(actual, "norm")    print(x)The Null hypothesis used here assumes that the numbers follow the normal distribution. It returns statistics and p-value. If the p-value is < alpha, we reject the Null hypothesis.Alpha is defined as the probability of rejecting the null hypothesis given the null hypothesis(H0) is true. For most of the practical applications, alpha is chosen as 0.05.Gain and Lift ChartGain or Lift is a measure of the effectiveness of a classification model calculated as the ratio between the results obtained with and without the model. Gain and lift charts are visual aids for evaluating the performance of classification models. However, in contrast to the confusion matrix that evaluates models on the whole population gain or lift chart evaluates model performance in a portion of the population.The higher the lift (i.e. the further up it is from the baseline), the better the model.The following gains chart, run on a validation set, shows that with 50% of the data, the model contains 90% of targets, Adding more data adds a negligible increase in the percentage of targets included in the model.Gain/lift chartLift charts are often shown as a cumulative lift chart, which is also known as a gains chart. Therefore, gains charts are sometimes (perhaps confusingly) called “lift charts”, but they are more accurately cumulative lift charts.It is one of their most common uses is in marketing, to decide if a prospective client is worth calling.Gini CoefficientThe Gini coefficient or Gini Index is a popular metric for imbalanced class values. The coefficient ranges from 0 to 1 where 0 represents perfect equality and 1 represents perfect inequality. Here, if the value of an index is higher, then the data will be more dispersed.Gini coefficient can be computed from the area under the ROC curve using the following formula:Gini Coefficient = (2 * ROC_curve) — 1ConclusionUnderstanding how well a machine learning model is going to perform on unseen data is the ultimate purpose behind working with these evaluation metrics. Metrics like accuracy, precision, recall are good ways to evaluate classification models for balanced datasets, but if the data is imbalanced and there’s a class disparity, then other methods like ROC/AUC, Gini coefficient perform better in evaluating the model performance.Well, this concludes this article. I hope you guys have enjoyed reading it, feel free to share your comments/thoughts/feedback in the comment section.Thanks for reading !!!

Machine Learning
The Role of AI in Unstructured Data Mining: Challenges and Opportunities

In our fast-paced digital world, we're producing staggering volumes of data every day. This data falls into two key categories: structured, known for its order and efficiency, and unstructured, a captivating puzzle brimming with untapped potential.In this article, we will uncover how AI confronts the complexities of unstructured data, the hurdles it faces, and the intriguing opportunities it opens up to businesses from any kind of industry.Understanding Unstructured DataUnstructured data mining is the technique of extracting valuable and meaningful insights from an abundant well of unstructured data. It uncovers hidden gems of knowledge, making it a crucial pursuit in our data-rich era.In today's digital realm, unstructured data is generated in unprecedented quantities. Billions of text documents, images, and videos come to life daily, creating a treasure trove of information just waiting for organizations to explore.Unlocking the insights hidden within unstructured data can provide organizations with a competitive edge. This data can reveal customer sentiments, emerging trends, and valuable feedback that might otherwise go unnoticed.The Basics of Data MiningHow data mining works is that it discovers patterns, trends, and valuable information within a dataset. It involves various techniques to extract knowledge from raw data. While it's exceptionally effective with structured data, applying data mining to unstructured data requires a unique set of skills and tools.Unstructured Data MiningUnstructured data mining is a method focused on the extraction of valuable information from the vast, unstructured data available. This process uncovers hidden insights, making it a valuable endeavor in today's data-driven world.The AI RevolutionThe AI revolution has given rise to an exciting era of possibilities in unstructured data mining. AI's remarkable capabilities are instrumental in taming the unstructured data landscape, and it involves a multitude of components, including:Machine learning enables AI systems to learn from data, make predictions, and identify patterns, enhancing data mining capabilities.Deep learning uses neural networks to model complex patterns in unstructured data, which is particularly valuable in image and speech recognition.Sentiment analysis gauges emotional tones within textual data, helping to understand public opinion and tailor strategies.Pattern recognition identifies recurring structures in data, aiding in image processing and text mining.Knowledge graphs structure data relationships, improving contextual understanding and data retrieval.Anomaly detection identifies outliers in data, which is essential for fraud detection and data security.Challenges in Unstructured Data MiningAs promising as AI is at handling unstructured data, it's not without its set of challenges. Here, we delve into some of the major hurdles:Data QualityUnstructured data is inherently messy. It's laden with errors, inconsistencies, and biases, which makes it a challenge to extract meaningful insights from this data. AI systems need to be trained rigorously to navigate and decipher this diversity in data quality. Techniques like data cleansing, normalization, and the use of context are essential in ensuring that AI systems provide accurate results.ScalabilityAs the volume of unstructured data grows, AI systems must scale to handle the data influx effectively. Traditional hardware and algorithms might not be sufficient to handle this data influx. Scalable infrastructure and distributed computing become crucial to ensuring that AI systems can process and analyze vast amounts of data efficiently.Privacy ConcernsMining unstructured data often raises ethical questions regarding privacy and data protection. That’s why it’s essential to strike the right balance between data utilization and respecting individual privacy. It's a challenge to ensure that AI systems are used responsibly and in compliance with data protection laws and regulations, such as GDPR in Europe. Techniques like anonymization and consent management play a vital role in addressing these privacy concerns.Opportunities and ApplicationsAI's role in unstructured data mining has opened up a world of opportunities across various industries. Let's explore some of the most promising applications:Customer InsightsUnstructured data, particularly sourced from social media and customer reviews, serves as a goldmine of information on customer behavior and preferences. By leveraging AI algorithms, companies can analyze sentiments, spot emerging trends, and even forecast future buying patterns. With these insights, they can fine-tune their marketing strategies, product development, and customer service to align with their ever-evolving audience's demands.Healthcare DiagnosisThe abundance of unstructured data found in medical records, radiological images, and wearable device data holds the key to transformative advancements. AI-powered systems, known for their proficiency in the analysis of this data, not only facilitate early disease detection but also provide highly individualized treatment plans, ultimately raising the standard of patient care. For example: AI expedites the process of analyzing medical images for anomalies, resulting in a significant reduction in the time required for diagnosing and treating severe conditions.Fraud DetectionWhen it comes to financial institutions, AI is a vital tool for exposing fraudulent activities that often hide within the vast volumes of unstructured transaction data. Through a meticulous examination of transaction patterns and anomalies, AI systems can rapidly pinpoint fraudulent actions, providing businesses with a robust defense against significant financial losses. The ability to detect and thwart fraud in real-time provides a critical advantage, resulting in annual savings of billions of dollars for businesses.ConclusionThe future belongs to those who embrace the AI revolution in unstructured data mining. In this future, data isn't just information; it's the key to success. So, let's move forward, embracing this tomorrow, where possibilities are limitless and opportunities are endless.

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