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

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

compare:

Rows: 8384
Columns: 9102

...

Rows: 1
Columns: 1
Total Cells: 1

Hamish