William,

Thanks. I adapted your example by doing:
  library(psych)
  pdf(file="myfile.pdf",width=30,height=30)
  pairs.panels(data,gap=0)
  dev.off()

The R part worked. I could see it doing so when I replaced the call to 'pdf' by
  windows(width=30,height=30)
. The remaining problem was that Adobe Reader only displayed ten rows of my file, and then hung. That doesn't surprise me, because it's an unreliable piece of software, often hanging on PDFs I find on Google. Annoying, though.

Jocelyn Paine
http://www.j-paine.org
http://www.spreadsheet-parts.org
+44 (0)7768 534 091

On Tue, 31 Aug 2010, William Revelle wrote:

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
It is 6 minutes to midnight     http://www.thebulletin.org


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