[R] Making plots in big scatterplot matrix large enough to see

[Greg Snow]

Look at the pairs2 function in the TeachingDemos package, this lets you produce smaller portions of the total scatterplot matrix at a time (with bigger plots), you could print the smaller portions then assemble the full matrix on a large wall, or just use it to look at potentially interesting parts.

-- 
Gregory (Greg) L. Snow Ph.D.
Statistical Data Center
Intermountain Healthcare
greg.snow at imail.org
801.408.8111


> -----Original Message-----
> From: r-help-bounces at r-project.org [mailto:r-help-bounces at r-
> project.org] On Behalf Of Jocelyn Paine
> Sent: Monday, August 30, 2010 10:21 PM
> To: r-help at r-project.org
> Subject: [R] Making plots in big scatterplot matrix large enough to see
> 
> I've got a data frame with 23 columns, and wanted to plot a scatterplot
> matrix of it. I called
>    pairs( df )
> where 'df' is my data frame. This did generate the matrix, but the
> plotting window did not expand to make the individual plots large
> enough
> to see. Each one was only about 10 pixels high and wide.
> 
> I tried sending the plot to a file, with a high and wide image,
> by doing
>    png( "plot.png", width = 4000, height = 4000 )
> but I got these errors:
>    Error in png( "plot.png", width = 4000, height = 4000 ) :
>    unable to start device
>    In addition: Warning messages:
>    1: In png( "plot.png", width = 4000, height = 4000 ) :
>       Unable to allocate bitmap
>    2: In png( "plot.png", width = 4000, height = 4000 ) :
>       opening device failed
> 
> The messages aren't helpful, because they don't tell you _why_ R can't
> start the device, allocate it, or open it. The documentation for png
> says:
>    Windows imposes limits on the size of bitmaps: these are not
> documented
>    in the SDK and may depend on the version of Windows. It seems that
> width
>    and height are each limited to 2^15-1.
> However, 2^15-1 is 32767, so that isn't the problem here. I tried
> various
> values for height and width. 2400 was OK, but 2500 wasn't. So it seems
> R
> can't produce plots that are more than about 2400 pixels square. This
> is
> with R 2.10.1.
> 
> Why is png failing on big images? Also, what's the recommended way to
> make
> a file containing a scatterplot matrix when you have lots of variables?
> 'pairs' is a very useful function, but obviously one does need to be
> careful when doing this, and I don't know what experts would recommend.
> Do
> you loop round the variables plotting each pair to a different file? I
> was
> hoping that I could put them all into one very big image and view parts
> of
> it at a time.
> 
> Thanks,
> 
> Jocelyn Paine
> http://www.j-paine.org
> http://www.spreadsheet-parts.org
> +44 (0)7768 534 091
> 
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