When I run the example in R 1.6.2, and view it with gs, I get a good plot. When I run the example in R 1.7.0, and view it with gs, I get a bad plot. (run on the same host)
My "bad plot" is as described by Stephen.
In the "good" postscript file, about 100 lines in, there is this: %%EndProlog %%Page: 1 1 bp 77.04 91.44 743.76 534.96 cl 0.0000 0.0000 0.0000 rgb 0.75 setlinewidth [] 0 setdash np 101.73 313.20 m 101.74 313.21 l 101.74 313.23 l 101.74 313.24 l 101.75 313.25 l (followed by ~200000 lines of the same type, with slowly changing values)
In the "bad" postscript file, at about the same point in the file, is this: %%EndProlog %%Page: 1 1 bp 77.04 91.44 743.76 534.96 cl 0 0 0 rgb 0.75 setlinewidth [] 0 setdash np 101.73 313.20 m 0.00 0.01 l 0.00 0.01 l 0.00 0.01 l 0.00 0.01 l 0.00 0.01 l (followed by ~200000 lines, including some like these)
0.00 0.00 l 0.00 0.00 l
0.00 -0.01 l 0.00 -0.01 l
0.00 -0.00 l 0.00 -0.00 l
Looks like it might be a formatting issue on how these lines were written.
My version information:
---- 1.6.2 ----
versionplatform sparc-sun-solaris2.7
arch sparc os solaris2.7 system sparc, solaris2.7 status major 1 minor 6.2 year 2003 month 01 day 10 language R
---- 1.7.0 ----
version_ platform sparc-sun-solaris2.7
arch sparc os solaris2.7 system sparc, solaris2.7 status major 1 minor 7.0 year 2003 month 04 day 16 language R
[245]% gs --version 5.50
-Don
At 5:59 PM +0100 5/29/03, Stephen Eglen wrote:
Hi,
I have a query about the maximum length of vector that can be plotted in one go in a postscript driver. Try the following code (in 1.7.0; version details below):
t <- seq(from=0, to=4*pi, length=200000) y <- sin(t) postscript(file="o.ps") plot(t, y, type="l") dev.off()
If I view the postscript file o.ps in "gv", it takes many seconds before eventually the axes appear, but then only one vertical line is drawn within the plot area -- there is no sine curve. (this is on a fast dual processor linux machine with 2Gb RAM.) This is clearly a postscript problem, rather than a R problem, since reducing the length of t down to something like 2000 solves the problem. By looking at the file o.ps it looks like the line is drawn by one "rlineto" call per point, followed eventually by a "stroke" after the last point. I'm guessing that the postscript interpreter simply cannot remember so many points in the path before it gets to the stroke.
The example above is artificial, but this problem appeared with a real data set this morning. The fix was to replace the single call to plot() with many calls to line(), breaking the t and y vectors into more manageable chunks; in this way, each postscript path was manageable and we got the plot.
I tried plotting the same long vectors in gnuplot by first writing them from R:
write.table(cbind(t,y), sep="\t", file="eg.dat", row.names=F, col.names=F, quote=F)
and then in gnuplot:
set term postscript set output "gnuplot.ps" plot "eg.dat" wi lines
This came out fine; in gnuplot.ps every 400 lines during the plot it outputs "currentpoint stroke M" (M is defined to moveto). I had a look at the gnuplot source (gnuplot-3.7.3/term/post.trm) and found that it does keep count of the length of the current postscript path: e.g. in the function PS_vector(x,y) we see (line 1122):
if (ps_path_count >= 400) { fprintf(gpoutfile,"currentpoint stroke M\n"); ps_path_count = 0; }
so every 400 points it draws the line so far and then continues. (Matlab .ps files also seem to have regular "MP stroke".
I had a quick look in the corresponding R code src/main/devPS.c and could not see any counter. Would it be worth adding such a counter and periodic line output to PS_Polyline?
versionplatform i686-pc-linux-gnu
arch i686 os linux-gnu system i686, linux-gnu status major 1 minor 7.0 year 2003 month 04 day 16 language R
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-- -------------------------------------- Don MacQueen Environmental Protection Department Lawrence Livermore National Laboratory Livermore, CA, USA
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