[GRASS-dev] Re: New module v.surf.trend but with external dependencies and ccmath problem

Roger Bivand Roger.Bivand at nhh.no
Tue May 4 13:00:27 EDT 2010

Hi Jarek,

Are you rescaling the coordinates before powering them? I see that you are
making some conversions in main.c, but they may not be enough. Try using the
unit square 0,1 instead, for example (x_i - min(x))/(max(x) - min(x)) or
something like this. Or see dscale() in the recommended R package
spatial/src/krc.c around line 452, which uses -1, 1 for the same reason, for
a code example.


Roger Bivand
Economic Geography Section
Department of Economics
Norwegian School of Economics and Business Administration
Helleveien 30
N-5045 Bergen, Norway

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