[GRASS-user] Raster map Calculator

GRASS GRASS user
1

Hello list,

I am trying to create a series of ratio images using grass 6.4.1 and I can’t get the syntax for the raster calculator figured out.
What I’ve got at the moment is:

‘Bar45rastfl = 1.0 * BarB40@PERMANENT / BarB50@PERMANENT’

I’ve tried varying the equation above but to no avail. The resulting maps do not contain any values.

What am I doing wrong?

Thanks in advance,

Regards,

Michiel

2

On 19/03/12 20:42, Michiel Kunzel wrote:

Hello list,

I am trying to create a series of ratio images using grass 6.4.1 and I
can't get the syntax for the raster calculator figured out.
What I've got at the moment is:

'Bar45rastfl = 1.0 * BarB40@PERMANENT / BarB50@PERMANENT'

I've tried varying the equation above but to no avail. The resulting
maps do not contain any values.

What am I doing wrong?

Have you set your region correctly ?

I.e. g.region rast=BarB40

before running r.mapcalc ?

Moritz

3

Solved!

I don’t know whether this was the region, it seemed set valid, re-set it just to be sure.
Gave the same confusing result at first, but might have been the color table set wrong.
The results appeared to be integer with just one value, but resetting the colour table and performing a stretch gave readable results.

Thank you for your help.

Michiel

Date: Tue, 20 Mar 2012 09:13:35 +0100
From: mlennert@club.worldonline.be
To: mich_kun@hotmail.com
CC: grass-user@lists.osgeo.org
Subject: Re: [GRASS-user] Raster map Calculator

On 19/03/12 20:42, Michiel Kunzel wrote:

Hello list,

I am trying to create a series of ratio images using grass 6.4.1 and I
can’t get the syntax for the raster calculator figured out.
What I’ve got at the moment is:

‘Bar45rastfl = 1.0 * BarB40@PERMANENT / BarB50@PERMANENT’

I’ve tried varying the equation above but to no avail. The resulting
maps do not contain any values.

What am I doing wrong?

Have you set your region correctly ?

I.e. g.region rast=BarB40

before running r.mapcalc ?

Moritz