Strange behaviour of image (PR#510)
Hi Peter,
On 6 Apr 2000, Peter Dalgaard BSA wrote:
J.C.Rougier@durham.ac.uk writes:
The following commands z <- matrix(seq(0, 1, len=1000)) image(z, 1, z, zlim=c(0, 1), col=gray(1:10/10)) appear to violate the image functionality as described on the help page. As I understand it, by specifying a zlim of c(0, 1) and a colour vector of length 10, the colours should correspond to the intervals (0, 0.1), (0.1, 0.2), ..., (0.9, 1.0), this being 10 equally-spaced intervals on (0, 1). It is clear from the image that this has not occurred. In fact the intervals are apparently (0, 1/18), (1/18, 3/18), ..., (15/18, 17/18), (17/18, 1). Have I misunderstood something?
I don't see that anything else is being promised... If someone actually thought about this, then the choice might be related to the behavior at peaks and troughs. (since a circle with radius r looks wide compared to the region between two circles with diameter n*r and (n+1)*r)
I'm not quite sure I follow. My feeling is that the displayed behaviour of image is unreasonable, and, I hazard, not what most people who use image expect. I think the default behaviour of image should be to give colour bands of equal widths, and, if I may append to the wish list, I woud like to be able to specify a "breaks" argument to have unequal widths should I so choose. Cheers, Jonathan. Jonathan Rougier Science Laboratories Department of Mathematical Sciences South Road University of Durham Durham DH1 3LE http://www.maths.dur.ac.uk/stats/people/jcr/jcr.html -.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.- r-devel mailing list -- Read http://www.ci.tuwien.ac.at/~hornik/R/R-FAQ.html Send "info", "help", or "[un]subscribe" (in the "body", not the subject !) To: r-devel-request@stat.math.ethz.ch _._._._._._._._._._._._._._._._._._._._._._._._._._._._._._._._._._._._._._._._