On 21-Jul-08 12:43:47, Duncan Murdoch wrote: > On 7/21/2008 8:13 AM, (Ted Harding) wrote: >> Hi Folks, >> I've been digging for the solution to this for several >> hours now. If there is a solution, it must be one of the >> worst "needle-in-a-haystack" examples in R documentation! >> >> Essentially, I want to make an x-y plot in which the >> X-axis really is the X-axis (i.e. its vertical position >> is at y=0), and the Y-axis really is the Y-axis (i.e. >> its horizontal position is at x=0). Discussion, with >> toy examples, below. >> >> I have sort-of solved this (as stated) for one special >> case, after a depth-4 search through >> >> ?plot --> ?plot.default --> ?par --> ?axis >> >> which finally led me to the parameter "pos" to axis(): >> >> ?axis >> pos: the coordinate at which the axis line is to be drawn: >> if not 'NA' this overrides the values of both 'line' and 'mgp[3]'. >> >> Hence, instead of >> >> plot(c(0.5,2.5),c(0.5,2.5),xlim=c(0,3),ylim=c(0,3), >> frame.plot=FALSE) >> >> (where the axes do not meet at the origin (0,0)), I can do >> >> plot(c(0.5,2.5),c(0.5,2.5),xlim=c(0,3),ylim=c(0,3), >> frame.plot=FALSE,pos=0) >> >> which is *exactly* what I want in this case. >> >> But now I want to do the same, where instead of plotting the >> two points (0.5,0.5), (2.5,2.5) I want to plot (0.5,2.5), (2.5,4.5). >> >> Provided I keep the xlim and ylim to both have lower value 0, >> a similar solution again works fine: >> >> plot(c(0.5,2.5),c(2.5,4.5),xlim=c(0,3),ylim=c(0,5), >> frame.plot=FALSE,pos=0) >> >> But, in this case, what I *really* want is to limit the Y range >> to the "relevant" bit: ylim=c(2,5) -- I don't want to have a lot >> of empty space below the points. So I want a Y-axis running from >> y=2 to y=5, and X-axis as before from x=0 to x=3, and I want these >> two axes to meet at (x=0,y=2). But how? >> >> By analogy to the above, I need to set a "pos=0" for the X-axis, >> and a "pos=2" for the y-axis. And I have not been able to discover >> how to do this. > > It may or may not be possible in a single call to plot(), but it is > certainly straightforward if you use separate calls to plot() and axis: > > > plot(c(0.5,2.5),c(2.5,4.5),xlim=c(0,3),ylim=c(2,5), axes=F) > > axis(1, pos=2) > > axis(2, pos=0)
Thanks, Duncan! That nicely rounds off Marc's response, and makes sense (and also, in fact, exposes my "blind spot" when I was reading the documentation in the first place). > Generally speaking I find it is usually easier not to try to convince > plot() to do strange things: I tell it to do nothing, and do the > strange things myself. It depends what you mean by "strange", Duncan. To be frank, I find R's default "offset" axes to be strange, and what I've been trying to achieve to be "normal". But that's a matter of taste, I suppose -- unless you need, for instance, to be able to lay a ruler over the plot and see where it meets the "axis"! > Duncan Murdoch Ted. -------------------------------------------------------------------- E-Mail: (Ted Harding) <[EMAIL PROTECTED]> Fax-to-email: +44 (0)870 094 0861 Date: 21-Jul-08 Time: 14:00:58 ------------------------------ XFMail ------------------------------ ______________________________________________ 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.
