## Is feature selection a dimensionality reduction technique?

Feature Selection vs Dimensionality Reduction While both methods are used for reducing the number of features in a dataset, there is an important difference.

Feature selection is simply selecting and excluding given features without changing them.

Dimensionality reduction transforms features into a lower dimension..

## What is the best feature selection method?

Embedded methods combine the qualities’ of filter and wrapper methods. It’s implemented by algorithms that have their own built-in feature selection methods. Some of the most popular examples of these methods are LASSO and RIDGE regression which have inbuilt penalization functions to reduce overfitting.

## Does PCA reduce Overfitting?

Though that, PCA is aimed to reduce the dimensionality, what lead to a smaller model and possibly reduce the chance of overfitting. So, in case that the distribution fits the PCA assumptions, it should help. To summarize, overfitting is possible in unsupervised learning too. PCA might help with it, on a suitable data.

## Is PCA feature selection or feature extraction?

Note that if features are equally relevant, we could perform PCA technique to reduce the dimensionality and eliminate redundancy if that was the case. Here we would be doing feature extraction, as we were transforming the primary features and not just selecting a subset of them.

## When should you not use PCA?

PCA should be used mainly for variables which are strongly correlated. If the relationship is weak between variables, PCA does not work well to reduce data. Refer to the correlation matrix to determine. In general, if most of the correlation coefficients are smaller than 0.3, PCA will not help.

## How Principal component analysis is used for feature selection?

A feature selection method is proposed to select a subset of variables in principal component analysis (PCA) that preserves as much information present in the complete data as possible. The information is measured by means of the percentage of consensus in generalised Procrustes analysis.