Question

Can PCA be used for supervised learning???

I've seen some data scientists using PCA to transform their data for only numerical variables.

However, some other data scientists say that it is only used for unsupervised ML techniques.

Answer 1

PCA can be used indirectly in supervised learning tasks such as classification and regression. When you have huge number of features, one way to reduce the number of features and probably avoid overfitting is using a feature reduction method such as PCA. Therefore, PCA can be used in preprocessing step to reduce the number of features.