[R] png() and/or jpeg(): line missing by using box(which="outer")

Prof Brian Ripley ripley at stats.ox.ac.uk
Sun Nov 2 14:44:12 CET 2003

I have an answer for the first of these.  box("outer") tries to draw a
polyline at (0,0), (0,1), (1,1), (1,0), (1,0) in device coordinates. Due
to rounding error, 1 was being plotted at pixel 480, and there are
only pixels 0...479.

This *was* also happening on screen, but for the default screen size on my 
machine it was being rounded down and so shown correctly.

I have added a `fuzz' to ensure 1 gets mapped to pixel 479.

On Tue, 21 Oct 2003, Pfaff, Bernhard wrote:

> Dear R list,
> I do encounter the following problem by generating either a png-file
> (example below) or a jpeg-file: 
> By employing 'box(which="outer")' a box is drawn, except for the right line.
> If I generate the plot without the 'box(which="outer")', a line at the
> bottom in the graphics file still appears. However, both plots are displayed
> correctly in the R Graphics Device Window, i.e  with a box including the
> right side or one without any lines at the outer margins of the plot. Now, I
> want either a file - including the right side of box or one that has none on
> all sides. 
> test <- rnorm(100)
> par(mar=c(6,4,6,4), oma=c(1,1,1,1))
> png("test1.png")
> plot(test)
> grid()
> box(which="outer")
> box(which="plot")
> dev.off()
> png("test2.png")
> plot(test)
> grid()
> box(which="plot")
> dev.off()
> Incidentally, both functions are calling .Internal(devga(....)). I have not
> encountered this problem with version R 1.7.1 (for which I used the binary
> distribution on CRAN). Now, I have source compiled R 1.8.0. Although,
> everything passed 'make check', I am wondering if it could be possible that
> 'devga.c' or any other necessary file for running png() or jpeg() have not
> been compiled 'correctly', or do I have simply to adjust a par()-argument?  
> Any pointers or help is appreciated.
> Bernhard
> platform: "i386-pc-mingw32"
> arch: "i386"
> os: "mingw32"
> system: "i386, mingw32"
> major: "1"
> minor: "8.0"
> Windows NT 5.0
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Brian D. Ripley,                  ripley at stats.ox.ac.uk
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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