Gilles, Both histogram1 and histogram2 can be plotted with the bar type, which I believe has colored bars.
The problem being addressed mostly with the verb named 'relative' on the wiki page is the situation where the bins are of different width. In that case I could only find a line type drawing to correctly represent the areas that are usually bars and could not color those bars. But most simple frequency graphs have equal bins and can be readily plotted with the bar type. ---------------------------------------------------------------------- For information about J forums see http://www.jsoftware.com/forums.htm
