[R] "Error in plot.window(...) : invalid 'xlim' value" from plot(...par(new = TRUE))

[David Wolfskill]

[New to the community; still in early part of R's learning curve.]

Several months ago, I was requested to generate some graphs on a
periodic basis.  Accordingly, I managed to figure out a way to do so,
using a combination of Perl and R (in a FreeBSD environment).

While I've needed to adjust a few things here and there, the general
approach has been pretty solid , and the R part has had very little
change perceived as necessary.

I re-generate the graphs each Wednesday morning (as they show disk space
utilization over time).

This morning, one of the graphs -- the first that used plot() with
"par(new = TRUE)" reported an error.  Re-doing the work interactively,
I was able to re-create the problem.  Poking around with
debug(plot.window) showed that while the ylim values make sense,
the xlim values are ... of an unexpected type altogether.

And when I re-tried the plot() invocation, but without the "par()"
argument, the xlim passed to plot.window() was fine, and the plot was
OK.

The data look like:

          Tag          Cap  mean_GB median_GB census
1  2010-02-03 540972711754 213.5250  154.1011   1061
2  2010-02-10 531711798208 169.4235  124.3809   1033
3  2010-02-17 544482444926 171.2384  130.0641   1052
...
52 2011-01-26 558625618800 195.2759  175.1277   1386
53 2011-02-02 571187807274 199.4980  170.4478   1406
54 2011-02-09 562448031310 197.5468  166.8976   1367

I'm trying to generate a plot, then overlay 3 more plots on it -- which
has been working for several months:

> plot(Is_total$Tag, Is_total$Cap/1024/1024/1024, type = "l", col = "blue", ylim = c(0, max(Is_total$Cap/1024/1024, Is_total$census * 400)/1024), xlab = "Date", ylab = "Capacity(TB)", main = "Total Local Disk Space")
> debug(plot.window)
>  plot(Is_total$Tag, (Is_total$census * Is_total$mean)/1024, type = "l", col = "green", ylim = c(0, max(Is_total$Cap/1024/1024, Is_total$census * 400)/1024), ann = FALSE, axes = FALSE, par(new = TRUE))
debugging in: plot.window(...)
debug: .Internal(plot.window(xlim, ylim, log, asp, ...))
Browse[2]> ylim
[1]   0.0000 549.2188
Browse[2]> xlim
$new
[1] FALSE

Browse[2]> c
Error in plot.window(...) : invalid 'xlim' value
> sessionInfo()
R version 2.12.1 (2010-12-16)
Platform: i386-portbld-freebsd8.2 (32-bit)

locale:
[1] C

attached base packages:
[1] stats     graphics  grDevices utils     datasets  methods   base     
>  plot(Is_total$Tag, (Is_total$census * Is_total$mean)/1024, type = "l", col = "green", ylim = c(0, max(Is_total$Cap/1024/1024, Is_total$census * 400)/1024), ann = FALSE, axes = FALSE)
debugging in: plot.window(...)
debug: .Internal(plot.window(xlim, ylim, log, asp, ...))
Browse[2]> ylim
[1]   0.0000 549.2188
Browse[2]> xlim
[1] 14643 15014
Browse[2]> c
exiting from: plot.window(...)
> q()

This is running on my laptop:
FreeBSD 8.2-PRERELEASE #99 r218478: Wed Feb  9 04:17:55 PST 2011     root at g1-222.catwhisker.org.:/common/S1/obj/usr/src/sys/CANARY 

(Yes, I track FreeBSD stable/8 on it daily.)

I built R as a FreeBSD port; it is version 2.12.1.  (I update the
installed ports daily, too.)

I actually first noticed the behavior on my desktop machine at work; it
is also running FreeBSD stable/8, but only updated as of 30 Jan 2011 --
and the problem did not exist last week.  So I don't believe this is
because of a change in FreeBSD.

For now, I'm (also) open to circumventions, so I can avoid complaints
about the graphs that weren't updated at work, but I'd like to resolve
the issue.  (And yes, I fully understand that what needs to be fixed is
my understanding of how to use the tools.)

Thanks!

Peace,
david
-- 
David H. Wolfskill				r at catwhisker.org
Depriving a girl or boy of an opportunity for education is evil.

See http://www.catwhisker.org/~david/publickey.gpg for my public key.
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