The following works in R-devel
x <- rnorm(1000)
hist(x, xlim=c(-4,4))
usr <- par("usr")
clip(usr[1], -2, usr[3], usr[4])
hist(x, col = 'red', add = TRUE)
clip(2, usr[2], usr[3], usr[4])
hist(x, col = 'blue', add = TRUE)
do.call("clip", as.list(usr)) # reset to plot region
I think that is a general enough mechanism -- see its help page for how
long one can expect a clipping region to persist.
On Fri, 22 Feb 2008, Prof Brian Ripley wrote:
> I think you misunderstand what par("plt") is supposed to do. The
> documentation says
>
> 'plt' A vector of the form 'c(x1, x2, y1, y2)' giving the
> coordinates of the plot region as fractions of the current
> figure region.
>
> You haven't subsequently made a new plot, so why do you expect the clipping
> region to be changed to that you indicated for the next plot?
>
> I'd say the bug was that box() changed it, and that happens because it
> internally sets xpd and so resetting xpd sets the clipping region next time
> it is used. Because of
>
> void GClip(pGEDevDesc dd)
> {
> if (gpptr(dd)->xpd != gpptr(dd)->oldxpd) {
> double x1, y1, x2, y2;
> setClipRect(&x1, &y1, &x2, &y2, DEVICE, dd);
> GESetClip(x1, y1, x2, y2, dd);
> gpptr(dd)->oldxpd = gpptr(dd)->xpd;
> }
> }
>
> Maybe we should have user-level code to set the clipping region?
>
>
> On Fri, 22 Feb 2008, Greg Snow wrote:
>
>> Here is a demonstration of behaviour that is probably an optimization by
>> someone far smarter than me that did not anticipate anyone wanting to do
>> this, but for my purposes it looks more like a bug than a feature.
>>
>> I have tested this with R2.6.2 on Windows, no additional packages loaded
>> (beyond the default), I have tested using the default graphics object,
>> pdf, jpeg, and cairoDevice (ok I loaded a package for that) and all show
>> the same behavior.
>>
>> Run the following set of commands:
>>
>> x <- rnorm(1000)
>> hist(x, xlim=c(-4,4))
>>
>> tmp <- par('plt')
>>
>> box(col='#00000000')
>> tmp2 <- tmp
>> tmp2[2] <- tmp2[1] + 0.3
>> par(xpd = FALSE, plt=tmp2)
>> hist(x, col='red', add=TRUE)
>>
>> box(col='#00000000')
>> tmp3 <- tmp
>> tmp3[1] <- tmp3[2] - 0.3
>> par(xpd=FALSE, plt=tmp3)
>> hist(x, col='blue', add=TRUE)
>> par(plt=tmp)
>>
>>
>> This gives me the plot that I want and expect (a histogram with the left
>> section red, the middle white/background, and the right blue).
>>
>> Now comment out or delete the 2 box commands and rerun everything. The
>> clipping does not happen this time and the final result is a full blue
>> histogram.
>>
>> Is this a bug? Feature? Something else?
>> Does anyone have a better work around than drawing transparent boxes?
>>
>> Thanks,
>>
>>
>>
>>
>
> --
> Brian D. Ripley, [EMAIL PROTECTED]
> Professor of Applied Statistics, http://www.stats.ox.ac.uk/~ripley/
> University of Oxford, Tel: +44 1865 272861 (self)
> 1 South Parks Road, +44 1865 272866 (PA)
> Oxford OX1 3TG, UK Fax: +44 1865 272595
>
--
Brian D. Ripley, [EMAIL PROTECTED]
Professor of Applied Statistics, http://www.stats.ox.ac.uk/~ripley/
University of Oxford, Tel: +44 1865 272861 (self)
1 South Parks Road, +44 1865 272866 (PA)
Oxford OX1 3TG, UK Fax: +44 1865 272595
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