[GRASS5] r.mapcalc question

[Jachym Cepicky]

what about r.patch?

else one could write some perl script, which would generate the sctring, full
    of 'if(isnull(.....' for mapcalc.

    Jáchym

On Wed, Feb 02, 2005 at 11:14:35AM -0800, David Piasecki wrote:
> Since I'm relatively new to GRASS, I just ran across the r.mapcalc  
> command, and I started playing with it for merging image data. I've  
> tried the following, some which works (but it's annoying) and some  
> which doesn't work but I'd like to know why. For both, assume the  
> region is set correctly.
> 
> First of all, what works:
> r.mapcalc  
> 'calc.red=if(isnull(image0.red),image1.red,if(isnull(image1.red),image0. 
> red))'
> 
> That's great; however, I have 42 images. So I tried some logic...
> r.mapcalc 'calc.red=( image0.red || image1.red )'
> r.mapcalc 'calc.red=( image0.red + image1.red )'
> 
> I think these aren't working because GRASS has a problem evaluating  
> these expressions since image0.red is null wherever image1.red is not  
> null. However, no error messages are given. Is there an easier way to  
> do this than the first command given above?
> 
> Thanks,
> David
> 
> 
> 
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-- 
Jachym Cepicky
e-mail: jachym.cepicky at centrum.cz
URL: http://les-ejk.cz
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