On Fri, 8 Aug 2014 06:26:35 AM carol white wrote: > Hi, > Is there any way to take one color of each color family from a color > palettes like rainbow? For ex, if there are different blues differentiated > by intensity, hue etc, taking one of them. In this case, when using > rainbow(n), then how to select 1 color of each family, for ex 1 blue, 1 red > etc? It doesn't matter which intensity, hue etc is taken as long as 1 color > from each family is taken. > > Hi Carol, Since you have asked a question about a fundamental aspect of graphic representation, I'll try to answer it. Be warned, it will be a rather discursive answer.
Whenever we try to communicate information about a number of things, where the information is different for each thing, it is essential to securely link the correct information to each thing. In compact graphic representations such as R plots, this usually resolves to labels of some sort. So we could construct a pie chart of the number of emails sent by each person in the present discourse using the names of the people involved. If we simply label each sector of the resulting plot with the names of the people, it will be reasonably informative in displaying each person's contribution. If we venture beyond the comfortable pale of the R help list and try to do this with something like Twitter, where I understand there may be thousands or even millions of contributors on a subject, the pie chart blurs into a chromatic dazzle with an unintelligible fringe of names. We might try to rescue the situation by aggregating the tweets into a few categories such as helpful, sarcastic and noise, but this does not solve the problem of how to display the comparative contributions of the twits involved. So one answer to your question of "How can I intelligibly label hundreds of things with colors?" may be "You can't unless your audience is made up of spectrographs." Plots that attempt to display information about too many things using line types, symbol types and colors often simply confuse the audience. My feeling is that it is the responsibility of the person choosing the method of communication to make sure that it communicates well. So if we want to display something meaningful about the hypothetical pandemonium of tweets above, we might choose to display the categories (helpful, sarcastic and noise) broken down by the sex of the twits. Perhaps in your case you might want to break down the functional category of the genes you are examining by the up- or down-regulation of those genes in different cell types. Your question touches things like "How many letters should there be in the alphabet?" and "How many acronyms for psychological tests can be meaningfully used in a paragraph?" At any rate, I thank you for giving me an idea about graphic illustration. Jim ______________________________________________ R-help@r-project.org mailing list https://stat.ethz.ch/mailman/listinfo/r-help PLEASE do read the posting guide http://www.R-project.org/posting-guide.html and provide commented, minimal, self-contained, reproducible code.
