[GRASS-user] r.mapcalc appears to have changed behavior

Hamish hamish_b at yahoo.com
Mon Sep 26 23:59:14 EDT 2011

Jim wrote:
> I had made a number of scripts that worked fine in the 6.4.0 build 6
> but appear to have problems with the same code in later revisions:
> The method used to take about 6-8 secs and produce about what you would
> expect on the screen. Now the same calculation takes 0 seconds the file
> is radically changed. See the before and after below.

the computational region is wrong. use g.region to fix it.

> r.mapcalc na_dem_sub_20 = na_dem_input - 20 

to match the region to the input map, first run:

  g.region rast=na_dem_input

>  Rows:         8384
>  Columns:      9102
> Rows:         1
> Columns:      1
> Total Cells:  1


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