I have RMA normalised file from microarray gene chip
I have 4 groups A,B,C,D(4 sample in group A , 5 sample in groups B, 3 samples in group C , 6 samples in group D) with 19K genes with there normalized value.
I need to perform PCA over this data.
How should i proceed with this ? as i do not have raw file so i cannot perform using Limma or other bioconductor packages so i need some other R based package or other open source tool.