Re: [R] contourLines() starts a plot device

From: Paul Murrell <p.murrell_at_auckland.ac.nz>
Date: Tue 21 Jun 2005 - 12:08:07 EST

Hi

Barry Rowlingson wrote:
> Pierre Kleiber wrote:
>

>> I want to use contourLines() to get contour line coordinate vectors, 
>> but I don't want to make a plot.  However contourLines() insists on
>> opening a graphics device.  Is there a way tell it not to do this?

>
>
> contourLines() calls .Internal(contourLines(...)), and that calls
> do_contourlines in plot3d.c, and that gets the current graphics device,
> hence activating one if there isn't one (I think), and passes it to
> GEcontourLines... which then seems to do nothing with it at all.
>
> I just removed 'dd' from the call to GEcontourLines and the arg list to
> GEcontourLines, fixed GraphicsEngine.h to match, recompiled, and now my
> contourLines() function doesn't try to make a new graphics window. I
> can't see GEcontourLines being called from anywhere else, but there may
> be code that calls it, so possibly a better idea may be to pass a NULL
> to it from GEcontourLines to keep the API the same.

Thanks for the diagnosis and suggested fix! This change has now been made in the development version of R.

Paul

> There are some comments scattered around the code about how
> contourLines shouldnt really be a graphics function, so I'm guessing
> there's some thought going into this already by the developers.
>
> Another possible quick fix for unix systems may be to start a
> PostScript graphics device with file="/dev/null" so that the graphics
> output disappears into thin air.
>
> Baz
>
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-- 
Dr Paul Murrell
Department of Statistics
The University of Auckland
Private Bag 92019
Auckland
New Zealand
64 9 3737599 x85392
paul@stat.auckland.ac.nz
http://www.stat.auckland.ac.nz/~paul/

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Received on Tue Jun 21 12:14:36 2005

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