Hi!

I am performing the quality control of some expression microarray data with oligo. I am plotting the densities of the signal for each sample with oligo::hist(). The plot is okay but, after reading oligo reference manual and matplot() function manual, I don't find how to show the legend. I would like to have a legend to know which density line refers to each sample, but I don't find how.

How can I achieve this? Thanks!

Those are just base R plots. So you can add a legend using the legend function.