[GRASS-dev] r.mapcalc bug on max and min?
wenzeslaus at gmail.com
Mon Oct 6 07:05:01 PDT 2014
On Mon, Oct 6, 2014 at 9:39 AM, Anna Petrášová <kratochanna at gmail.com>
> On Mon, Oct 6, 2014 at 9:07 AM, Pietro <peter.zamb at gmail.com> wrote:
>> On Mon, Oct 6, 2014 at 2:25 PM, Anna Petrášová <kratochanna at gmail.com>
>> > On Mon, Oct 6, 2014 at 4:51 AM, Pietro <peter.zamb at gmail.com> wrote:
>> >> Again everything is NULL, I'm doing something wrong or it is a bug?
>> > Glynn could perhaps give you some more precise comment, but basically,
>> > doesn't operate on the entire map but only on the current cell. So for
>> > example, r.macalc "map_max = max(elevation1, elevation2, elevation3)"
>> > creates a map where each cell is the largest value of the corresponding
>> > cells in the 3 elevation maps.
>> Ahh, I misunderstood the documentation I thought it was not pixel by
>> pixel but for the whole raster map...
>> now the results are explained! :-)
>> Perhaps we could add two new functions, like: rmin and rmax that stay
>> for range min and range max that give this information, do you think
>> could be useful?
> Yes, definitely, I was also missing this functionality. I assume it
> shouldn't be too difficult since range is stored in the map anyway.
This should strictly work on computational region.
Another function which I miss is coalesce which would use first non-NULL
value from the left but this is unrelated.
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