# Feature Selection

## Definition of Feature Selection

Feature Selection: Feature selection is the process of choosing which features (or attributes) of a data set to use in order to solve a problem. This is an important step in data science, as it can help reduce the complexity of a problem and improve the accuracy of predictions or models. There are a number of different techniques that can be used for feature selection, including:

• Scree Plots: A scree plot is a graphical tool used to identify important features in a data set. It is created by plotting the magnitude of each feature against its position on the X-axis. The features that have the largest impact on the solution will be located near the top of the plot, while those with less impact will be located towards the bottom.
• Mutual information: Mutual information is a measure of how important two features are to each other. It is calculated by taking the product of the conditional probabilities of each feature given the other, and then dividing it by the joint probability of both features. This metric can be used to determine whether two features are dependent or independent of each other.
• Correlation: Correlation is a measure of how strongly two features are related. It is calculated by taking the Pearson correlation coefficient, which ranges from -1 to 1. A value of 1 indicates that there is a perfect positive correlation between the two features, while a value of -1 indicates a perfect negative correlation.

## What is Feature Selection used for?

Feature selection is a process used to identify the most significant features of a dataset. It can be used to improve the accuracy of a machine learning model by eliminating irrelevant or redundant features that do not contribute useful information for model training. Feature selection reduces the complexity of the model and makes it easier to interpret, allowing for better predictive performance. Additionally, it can also reduce overfitting and improve generalization, which are both important aspects when creating models with good predictive accuracy on unseen data.

Feature selection involves identifying which variables have the strongest correlation with target variables and choosing only those variables for use in a predictive model. It can be done manually, through statistical tests such as analysis of variance (ANOVA), or using various algorithms such as recursive feature elimination, embedded methods, regularization methods (LASSO or ridge regression), or decision trees. Depending on the algorithm and feature set used, feature selection can greatly increase the speed and accuracy of a predictive model by reducing its complexity while still maintaining its high quality performance on unseen data.