[GRASS-user] MAP Calculator mean of eight neighbors to interpolate 0 value in raster map

[stephen sefick]

I must have made a miss-step because turning the 0 to null and then
used r.fillnulls.  Thanks everybody for there very helpful responses.
I did get to learn about mapcalc in the process.
kind regards,

Stephen Sefick

On Fri, Aug 28, 2009 at 5:21 PM, Glynn Clements<glynn at gclements.plus.com> wrote:
>
> stephen sefick wrote:
>
>> >> This does not quite work for my purposes.  The problem is the the 0
>> >> values are in a 2 or 3 grid wide seam in between patched raster maps,
>> >> so the value is lower than it should be using
>> >>
>> >> r.mapcalc "benning_dem=if(patch_benning==0,
>> >> (patch_benning[-1,-1]+patch_benning[1,-1]+patch_benning[-1,0]+
>> >> patch_benning[1,0]+patch_benning[-1,1]+patch_benning[1,1])/6,
>> >> patch_benning)"
>> >>
>> >> any thoughts,
>> >
>> > Do you want the average of all of the surrounding values, or only the
>> > non-zero values?
>>
>> only the no zero values.  I could probably do something like if
>> patch_benning[-1,-1]>0 etc., but I don not know how to code the number
>> of non-zero numbers in the divisor to get and average.
>
> r.mapcalc "benning_dem = eval( \
>        m = patch_benning, \
>        numer =  m[-1,-1]+ m[-1,0]+ m[-1,1]+ m[0,-1]+ m[0,1]+ m[1,-1]+ m[1,0]+ m[1,1], \
>        denom = !m[-1,-1]+!m[-1,0]+!m[-1,1]+!m[0,-1]+!m[0,1]+!m[1,-1]+!m[1,0]+!m[1,1], \
>        if(m,m,numer/denom))
>
> The "!" (logical "not") operator returns 1 if its operand is zero and
> 0 otherwise.
>
> --
> Glynn Clements <glynn at gclements.plus.com>
>



-- 
Stephen Sefick

Let's not spend our time and resources thinking about things that are
so little or so large that all they really do for us is puff us up and
make us feel like gods.  We are mammals, and have not exhausted the
annoying little problems of being mammals.

								-K. Mullis