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

[William Revelle]

Jocelyn,
   In a partial answer to your question, try setting gap=0 in the 
calls to pairs.  This will make the plots closer together.

  (You might also find pairs.panels in the psych package useful,  -- 
it implements one of the help examples for pairs to report the 
histogram on the diagonal and reports the correlations in the upper 
off diagonal).

On a Mac, I just tried setting
quartz(width=30, height=30)   #make a big graphics window


#then
library(psych)
my.data <- sim.item(24)  #create 500 cases of 24 variables
pairs.panels(my.data, gap=0)  #the gap =0 makes the plots right next 
to each other

#And then save the graphics window as a pdf.  I can open this in a 
pdf  and scroll around pretty easily.


Bill

At 5:21 AM +0100 8/31/10, Jocelyn Paine wrote:
>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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-- 
William Revelle		http://personality-project.org/revelle.html
Professor			http://personality-project.org
Department of Psychology             http://www.wcas.northwestern.edu/psych/
Northwestern University	http://www.northwestern.edu/
Use R for psychology                       http://personality-project.org/r
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