graphics bug: type="l" (PR#120)

[Prof Brian D Ripley]

On Tue, 16 Feb 1999 Matt Wiener, mcw@ln.nimh.nih.gov wrote:

> 
> The following commands illustrate a problem with graphing relatively large
> data sets using the "line" option to plot:
> 
> temp <- runif(200000)  # or whatever other numbers you like;
> 			# same thing happens with a sine wave
> plot(1:200000, temp)    # everything fine
> plot(1:200000, temp, type="l")   # data gets cut off
> 
> 
> The number of points isn't crucial.  The cutoff point appears to be about
> 65,000 points.  (70,000 points demonstrates the cutoff; with 50,000 points
> there's no cutoff.) 

This is device-specific (and which device was not mentioned). It does not
happen on Windows (rw0632) nor on a postscript device. It does happen on
the Unix x11() device for me, and my guess is that it is a limitation in
the X library used.  (Not in the X server, for this works in gs
displaying postscript, and in S-PLUS. The lines are drawn in a single Xlib
call.)

Do you really want to plot such a dataset in one go? What do you
expect to see of significance in 200000 points? (There are by default only 
about twice that many pixels on the device surface.) Are they really one
group? Would some group colour coding help? ....

-- 
Brian D. Ripley,                  ripley@stats.ox.ac.uk
Professor of Applied Statistics,  http://www.stats.ox.ac.uk/~ripley/
University of Oxford,             Tel:  +44 1865 272861 (self)
1 South Parks Road,                     +44 1865 272860 (secr)
Oxford OX1 3TG, UK                Fax:  +44 1865 272595

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