Book Image

The Data Science Workshop

By : Anthony So, Thomas V. Joseph, Robert Thas John, Andrew Worsley, Dr. Samuel Asare
Book Image

The Data Science Workshop

By: Anthony So, Thomas V. Joseph, Robert Thas John, Andrew Worsley, Dr. Samuel Asare

Overview of this book

You already know you want to learn data science, and a smarter way to learn data science is to learn by doing. The Data Science Workshop focuses on building up your practical skills so that you can understand how to develop simple machine learning models in Python or even build an advanced model for detecting potential bank frauds with effective modern data science. You'll learn from real examples that lead to real results. Throughout The Data Science Workshop, you'll take an engaging step-by-step approach to understanding data science. You won't have to sit through any unnecessary theory. If you're short on time you can jump into a single exercise each day or spend an entire weekend training a model using sci-kit learn. It's your choice. Learning on your terms, you'll build up and reinforce key skills in a way that feels rewarding. Every physical print copy of The Data Science Workshop unlocks access to the interactive edition. With videos detailing all exercises and activities, you'll always have a guided solution. You can also benchmark yourself against assessments, track progress, and receive content updates. You'll even earn a secure credential that you can share and verify online upon completion. It's a premium learning experience that's included with your printed copy. To redeem, follow the instructions located at the start of your data science book. Fast-paced and direct, The Data Science Workshop is the ideal companion for data science beginners. You'll learn about machine learning algorithms like a data scientist, learning along the way. This process means that you'll find that your new skills stick, embedded as best practice. A solid foundation for the years ahead.

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Table of Contents (18 chapters)
Preface
Preface
About the Book
1
1. Introduction to Data Science in Python
1. Introduction to Data Science in Python
Introduction
Application of Data Science
Overview of Python
Python for Data Science
Scikit-Learn
Summary
Free Chapter
2
2. Regression
2. Regression
Introduction
Simple Linear Regression
Multiple Linear Regression
Conducting Regression Analysis Using Python
Multiple Regression Analysis
Assumptions of Regression Analysis
Explaining the Results of Regression Analysis
Summary
3
3. Binary Classification
3. Binary Classification
Introduction
Understanding the Business Context
Feature Engineering
Data-Driven Feature Engineering
Correlation Matrix and Visualization
Summary
4
4. Multiclass Classification with RandomForest
4. Multiclass Classification with RandomForest
Introduction
Training a Random Forest Classifier
Evaluating the Model's Performance
Maximum Depth
Minimum Sample in Leaf
Maximum Features
Summary
5
5. Performing Your First Cluster Analysis
5. Performing Your First Cluster Analysis
Introduction
Clustering with k-means
Interpreting k-means Results
Choosing the Number of Clusters
Initializing Clusters
Calculating the Distance to the Centroid
Standardizing Data
Summary
6
6. How to Assess Performance
6. How to Assess Performance
Introduction
Splitting Data
Assessing Model Performance for Regression Models
Assessing Model Performance for Classification Models
The Confusion Matrix
Receiver Operating Characteristic Curve
Area Under the ROC Curve
Saving and Loading Models
Summary
7
7. The Generalization of Machine Learning Models
7. The Generalization of Machine Learning Models
Introduction
Overfitting
Underfitting
Data
Random State
Cross-Validation
cross_val_score
LogisticRegressionCV
Hyperparameter Tuning with GridSearchCV
Hyperparameter Tuning with RandomizedSearchCV
Model Regularization with Lasso Regression
Ridge Regression
Summary
8
8. Hyperparameter Tuning
8. Hyperparameter Tuning
Introduction
What Are Hyperparameters?
Finding the Best Hyperparameterization
Tuning Using Grid Search
GridSearchCV
Random Search
Summary
9
9. Interpreting a Machine Learning Model
9. Interpreting a Machine Learning Model
Introduction
Linear Model Coefficients
RandomForest Variable Importance
Variable Importance via Permutation
Partial Dependence Plots
Local Interpretation with LIME
Summary
10
10. Analyzing a Dataset
10. Analyzing a Dataset
Introduction
Exploring Your Data
Analyzing Your Dataset
Analyzing the Content of a Categorical Variable
Summarizing Numerical Variables
Visualizing Your Data
Boxplots
Summary
11
11. Data Preparation
11. Data Preparation
Introduction
Handling Row Duplication
Converting Data Types
Handling Incorrect Values
Handling Missing Values
Summary
12
12. Feature Engineering
12. Feature Engineering
Introduction
Merging Datasets
Binning Variables
Manipulating Dates
Performing Data Aggregation
Summary
13
13. Imbalanced Datasets
13. Imbalanced Datasets
Introduction
Understanding the Business Context
Challenges of Imbalanced Datasets
Strategies for Dealing with Imbalanced Datasets
Generating Synthetic Samples
Summary
14
14. Dimensionality Reduction
14. Dimensionality Reduction
Introduction
Creating a High-Dimensional Dataset
Strategies for Addressing High-Dimensional Datasets
Comparing Different Dimensionality Reduction Techniques
Summary
15
15. Ensemble Learning
15. Ensemble Learning
Introduction
Ensemble Learning
Simple Methods for Ensemble Learning
Summary
16
16. Machine Learning Pipelines
16. Machine Learning Pipelines
Introduction
Pipelines
Automating ML Workflows Using Pipeline
ML Pipeline with Processing and Dimensionality Reduction
ML Pipeline for Modeling and Prediction
ML Pipeline for Spot-Checking Multiple Models
ML Pipelines for Identifying the Best Parameters for a Model
Applying Pipelines to a Dataset
Summary
17
17. Automated Feature Engineering
17. Automated Feature Engineering
Introduction
Feature Engineering
Featuretools on a New Dataset
Summary

Assumptions of Regression Analysis

Due to the parametric nature of linear regression analysis, the method makes certain assumptions about the data it analyzes. When these assumptions are not met, the results of the regression analysis may be misleading to say the least. It is, therefore, necessary to check any analysis work to ensure the regression assumptions are not violated.

Let's review the main assumptions of linear regression analysis that we must ensure are met in order to develop a good model:

  1. The relationship between the dependent and independent variables must be linear and additive.

    This means that the relationship must be of the straight-line type, and if there are many independent variables involved, thus multiple linear regression, the weighted sum of these independent variables must be able to explain the variability in the dependent variable.

  2. The residual terms (ϵi) must be normally distributed. This is so that the standard error of estimate is calculated correctly. This standard error of estimate statistic is used to calculate t-values, which, in turn, are used to make statistical significance decisions. So, if the standard error of estimate is wrong, the t-values will be wrong and so are the statistical significance decisions that follow on from the p-values. The t-values that are calculated using the standard error of estimate are also used to construct confidence intervals for the population regression parameters. If the standard error is wrong, then the confidence intervals will be wrong as well.
  3. The residual terms (ϵi) must have constant variance (homoskedasticity). When this is not the case, we have the heteroskedasticity problem. This point refers to the variance of the residual terms. It is assumed to be constant. We assume that each data point in our regression analysis contributes equal explanation to the variability we are seeking to model. If some data points contribute more explanation than others, our regression line will be pulled toward the points with more information. The data points will not be equally scattered around our regression line. The error (variance) about the regression line, in that case, will not be constant.
  4. The residual terms (ϵi) must not be correlated. When there is correlation in the residual terms, we have the problem known as autocorrelation. Knowing one residual term, must not give us any information about what the next residual term will be. Residual terms that are autocorrelated are unlikely to have a normal distribution.
  5. There must not be correlation among the independent variables. When the independent variables are correlated among themselves, we have a problem called multicollinearity. This would lead to developing a model with coefficients that have values that depend on the presence of other independent variables. In other words, we will have a model that will change drastically should a particular independent variable be dropped from the model for example. A model like that will be inaccurate.

Activity 2.02: Fitting a Multiple Log-Linear Regression Model

A log-linear regression model you developed earlier was able to explain about 24% of the variability in the transformed crime rate per capita variable. You are now asked to develop a log-linear multiple regression model that will likely explain 80% or more of the variability in the transformed dependent variable. You should use independent variables from the Boston Housing dataset that have a correlation coefficient of 0.4 or more.

You are also encouraged to include the interaction of these variables to order two in your model. You should produce graphs and data that show that your model satisfies the assumptions of linear regression.

The steps are as follows:

  1. Define a linear regression model and assign it to a variable. Remember to use the log function to transform the dependent variable in the formula string, and also include more than one independent variable in your analysis.
  2. Call the fit method of the model instance and assign the results of the method to a new variable.
  3. Print a summary of the results and analyze your model.

    Your output should appear as shown:

Figure 2.19: Expected OLS results

Figure 2.19: Expected OLS results

Note

The solution to this activity can be found here: https://packt.live/2GbJloz.

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