Dear Roger, Thank you for your suggestion and explanation, that was v. helpful. I also found the axTicks() command to help generate the normal sequences for tick marks and labels used in your 'kludge' eg:
>plot(y=-y,x=x, ylim=range(-y), asp=1, axes=FALSE) >box() >axis(1) axis(2, at=axTicks(2), label=axTicks(2)*-1) Many thanks, Greg. On 5/3/05 7:19 pm, "Roger Bivand" <[EMAIL PROTECTED]> wrote: > On Sat, 5 Mar 2005, Gregory Jefferis wrote: > >> Dear R users, >> >> I would like to reverse the axes on some xy plots (for example to set the >> origin at the top left rather than the bottom left). I had planned to use >> something of the following form: >> >> plot(y=y<-c(20,4,5,6),x=x<-c(10,20,30,40),ylim=rev(range(y))) >> >> ie reversing ylim to reverse the y axis. This works fine however I also >> want to use the parameter asp=1 to ensure that equal distances in the x or y >> direction are plotted as such on the screen. However the simple example I >> showed above now fails: >> >>> plot(y=y<-c(20,4,5,6),x=x<-c(10,20,30,40),ylim=rev(range(y)),asp=1) >> >> The actual ylim used is considerably less than it should be, so no points >> appear on the plot. >> >> Can anyone suggest a simple remedy? > >> plot(y=-y,x=x, ylim=range(-y), asp=1, axes=FALSE) >> box() >> axis(1) >> axis(2, at=seq(-20,-5,5), label=seq(20,5,-5)) > > is a simple kludge, the explanation is touched on in a comment in > src/main/plot.c, after line 564: > > * The use of asp can have weird effects when axis is an > * interpreted function. It has to be internal so that the > * full computation is captured in the display list. > > and may be related to the sign of ydelta being dropped in line 652 (for > the y axis) and Gscale() being possibly called in line 666 with incorrect > assumptions about whether to add or subtract the correction factor - > untried! > >> >> Many thanks, >> >> Greg Jefferis. >> >> PS I would guess that the origin of this behaviour is that plot.window >> expects xlim (and ylim) to be in the order xmin,xmax (or ymin,ymax) when it >> sets about redefining xlim and ylim if asp!=NA. If that suggestion is >> correct, I'm not quite sure why the restriction is necessary. >> >> -- Gregory Jefferis, PhD and: Research Fellow Department of Zoology St John's College Downing Street Cambridge Cambridge, CB2 3EJ CB2 1TP Tel: +44 (0)1223 336683 +44 (0)1223 339899 Fax: +44 (0)1223 336676 +44 (0)1223 337720 [EMAIL PROTECTED] ______________________________________________ R-help@stat.math.ethz.ch mailing list https://stat.ethz.ch/mailman/listinfo/r-help PLEASE do read the posting guide! http://www.R-project.org/posting-guide.html
