Re: [Rd] Problems with plot and Quartz device

From: Simon Urbanek <simon.urbanek_at_r-project.org>
Date: Wed, 03 Jun 2009 07:45:40 -0400

On Jun 3, 2009, at 4:45 , tsr_at_stat.washington.edu wrote:

> Full_Name: Thomas Richardson
> Version: R 2.9.0 GUI 1.28 Tiger build 32-bit (5395)
> OS: 10.4.11
> Submission from: (NULL) (216.254.15.72)
>
>
>
> I have encountered a problem with points in scatterplots
> disappearing in a
> quartz window when it is re-sized (to make it larger).
>
> I am constructing an 8x12 matrix of scatterplots each containing
> approx 600
> points.
> In order to get them in the window I remove the axes etc.,
>
> quartz()
> par(mfrow=c(8,12), mar=c(0,0,0,0), oma=c(0,0,0,0))
> for(i in 1:8){ # Row counter
> for(j in 1:12){ # Col counter
> plot(rna$red[(rna$row==levels(rna$row[i])&(rna$col==j)],
> rna$tof[(rna$row==levels(rna$row[i])&(rna$col==j)],
> xlab="tof",ylab="green",xaxt="n",yaxt="n",
> ann=FALSE,xlim=c(0,100),ylim=c(0,300),pch=".")
> }
> }
>
> Here is the problem: how many data points actually appear in the
> quartz window
> on my screen is highly sensitive to the width and height specified.
> If I specify
> a different width and height for the quartz window e.g.
> quartz(width=8,height=8), OR if I resize the window with the cursor
> then points
> disappear in certain (x-axis) ranges across all the plots in some
> columns. These
> bands in which points disappear are the same for all plots in a
> given column,
> and can be very wide - making a lot of points disappear.
>
> (The visual effect is to make it look as if there are clearly
> defined vertical
> white lines going across the scatterplots - though the black lines
> enclosing
> each plot are not broken).
>
> The problem seems to disappear with other plotting symbols e.g.
> pch="+" (but
> then I end up with crowded plots).

BTW: you may want to use something like pch=19, cex=0.1 (and maybe add some alpha to get a quick density estimation).

Cheers,
S

> So I guess it might be related to the
> "special treatment" of "." described on help(points) ??
> ---
> Value pch="." (equivalently pch = 46) is handled specially. It is a
> rectangle of
> side 0.01 inch (scaled by cex).
> ---
>
> I find this behaviour unnerving: the (resized) plots made it look as
> if there
> was a lot of structure in the data, but on closer inspection it
> turned out to be
> entirely a consequence of the quartz device and plot function!
>
> I can't imagine that this behaviour is intended - even if it were
> intended to
> suppress points (like some axis labels) - it seems strange that
> enlarging the
> window makes points disappear. (I also tried setting dpi=72 in
> quartz(), but
> this did not fix the problem).
>
> Thanks in advance.
>
> Thomas
>
> ------------------------------------------------------
> sessionInfo()
> R version 2.9.0 (2009-04-17)
> i386-apple-darwin8.11.1
>
> locale:
> en_US.UTF-8/en_US.UTF-8/C/C/en_US.UTF-8/en_US.UTF-8
>
> attached base packages:
> [1] stats graphics grDevices utils datasets methods base
>
> ______________________________________________
> R-devel_at_r-project.org mailing list
> https://stat.ethz.ch/mailman/listinfo/r-devel
>
>



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