title: Categorizing samples in R, and plotting them in different colors
body: <p>I am new to learning R. I wanted to know how I can asssign a categorical value to observations I have read in as a dataframe. For eg I have data for m variables from n samples and I want to assign some samples as group 1 and some samples as group 2 and so on. Also, how can I visualise different groups in different colors when I plot them?</p>