I have 16 variables and I would like to use PCA to understand how they are correlated among each other’s. The first 8 variables (rates) have different units than the last 8 ones (times). After i used the code (as below) and created the biplot, I see the first 8 variables (rates) have an impact only. However, the rest of 8 variables (time) have small impact and I can’t see them on the graph. Does that happen because they are in different units? does PCA take care of variables when they are in different units? Is there a way to fix this? I'm positive these variables (time) should have a strong impact? Is there a way to fix this such as normalizing the data before running the code?
categories = ['r1';'r2';'r3';'r4';'r5';'r6';'r7';'r8';...
[coefforth,score,~,~,explainedVar] = pca(EF_Clu_Det(:,1:16));
biplot([coefforth(:,1) coefforth(:,2)],'Scores',[score(:,1) score(:,2)],'Varlabels',categories);