4. Classifying Data with scikit-learn
by Gavin Hackeling, Trent Hauck, Guillermo Moncecchi, Raúl Garreta
scikit-learn : Machine Learning Simplified
- scikit-learn: Machine Learning Simplified
- Table of Contents
- Credits
- Preface
- 1. Module 1
- 2. Module 2
- 1. Premodel Workflow
- Introduction
- Getting sample data from external sources
- Creating sample data for toy analysis
- Scaling data to the standard normal
- Creating binary features through thresholding
- Working with categorical variables
- Binarizing label features
- Imputing missing values through various strategies
- Using Pipelines for multiple preprocessing steps
- Reducing dimensionality with PCA
- Using factor analysis for decomposition
- Kernel PCA for nonlinear dimensionality reduction
- Using truncated SVD to reduce dimensionality
- Decomposition to classify with DictionaryLearning
- Putting it all together with Pipelines
- Using Gaussian processes for regression
- Defining the Gaussian process object directly
- Using stochastic gradient descent for regression
- 2. Working with Linear Models
- Introduction
- Fitting a line through data
- Evaluating the linear regression model
- Using ridge regression to overcome linear regression's shortfalls
- Optimizing the ridge regression parameter
- Using sparsity to regularize models
- Taking a more fundamental approach to regularization with LARS
- Using linear methods for classification – logistic regression
- Directly applying Bayesian ridge regression
- Using boosting to learn from errors
- 3. Building Models with Distance Metrics
- Introduction
- Using KMeans to cluster data
- Optimizing the number of centroids
- Assessing cluster correctness
- Using MiniBatch KMeans to handle more data
- Quantizing an image with KMeans clustering
- Finding the closest objects in the feature space
- Probabilistic clustering with Gaussian Mixture Models
- Using KMeans for outlier detection
- Using k-NN for regression
- 4. Classifying Data with scikit-learn
- Introduction
- Doing basic classifications with Decision Trees
- Tuning a Decision Tree model
- Using many Decision Trees – random forests
- Tuning a random forest model
- Classifying data with support vector machines
- Generalizing with multiclass classification
- Using LDA for classification
- Working with QDA – a nonlinear LDA
- Using Stochastic Gradient Descent for classification
- Classifying documents with Naïve Bayes
- Label propagation with semi-supervised learning
- 5. Postmodel Workflow
- Introduction
- K-fold cross validation
- Automatic cross validation
- Cross validation with ShuffleSplit
- Stratified k-fold
- Poor man's grid search
- Brute force grid search
- Using dummy estimators to compare results
- Regression model evaluation
- Feature selection
- Feature selection on L1 norms
- Persisting models with joblib
- 1. Premodel Workflow
- 3. Module 3
- 1. The Fundamentals of Machine Learning
- 2. Linear Regression
- 3. Feature Extraction and Preprocessing
- 4. From Linear Regression to Logistic Regression
- 5. Nonlinear Classification and Regression with Decision Trees
- 6. Clustering with K-Means
- 7. Dimensionality Reduction with PCA
- 8. The Perceptron
- 9. From the Perceptron to Support Vector Machines
- 10. From the Perceptron to Artificial Neural Networks
- Bibliography
- Index
This chapter will cover the following topics:
- Doing basic classifications with Decision Trees
- Tuning a Decision Tree model
- Using many Decisions Trees – random forests
- Tuning a random forest model
- Classifying data with support vector machines
- Generalizing with multiclass classification
- Using LDA for classification
- Working with QDA – a nonlinear LDA
- Using Stochastic Gradient Descent for classification
- Classifying documents with Naïve Bayes
- Label propagation with semi-supervised learning
Classification can be very important in a lot of contexts. For example, if we want to automate some decision-making process, we can utilize classification. In cases where we need to investigate a fraud, there are so many transactions that it is impractical for a person to check all of them. Therefore, we can automate such decisions with classification.
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