Bar Plot ggplot2 Filling bars with cross hatching
I disagree. Grey levels suck; labels are a kludge. It is an issue
for ``many'' == 2, for which crosshatching works perfectly.
Could you show an example? There are several BW examples in example(barplot), and the gray ones look better on screen than the cross-hatched one. (Not to say it makes a very good choice of cross-hatching, but I suspect the gray examples will look better than any 5 cross-hatch patterns.) I haven't tried printing the examples, so I'm not sure the gray would reproduce well on paper; I wouldn't try to print those 5 gray levels on a typical printer.
My feeling is that the best cross-hatching is probably going to be more aesthetically pleasing than the best solid greys (see e.g. http://www.dannygregory.com/2005/09/cross_hatching.php). However, doing cross hatching well is far more difficult than doing grey well, and for really nice cross-hatching I suspect you also need a high quality printer. It is also a challenging problem to come up with an algorithm for generating perceptually uniform sets of cross-hatchings. I suspect there is some work on this area in vis/infovis, but I haven't find it in a few minutes of casual searching. Hadley Hadley