Details Ticket 1338


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Serial Number 1338
Subject r.mapcalc results contain no data
Area bug
Queue grass
Requestors jzhao@ccermail.net
Owner none
Status resolved
Last User Contact Tue Oct 8 09:47:18 2002 (6 yr ago)
Current Priority 30
Final Priority 70
Due No date assigned
Last Action Tue Oct 8 09:47:20 2002 (6 yr ago)
Created Tue Oct 8 05:52:23 2002 (6 yr ago)

Transaction History Ticket 1338


Tue, Oct 8 2002 05:52:23    Request created by guest  
Subject: r.mapcalc results contain no data

Platform: WindowsNT/2000/XP
grass obtained from: Mirror of Trento site
grass binary for platform: Downloaded precompiled Binaries
GRASS Version: 5.0.0pre3

Hi,

I'm following the tutorial from "GRASS Seeds" at http://www.geog.le.ac.uk/assist/grass/seeds/.
The data set "leics" is also from there.
When using r.mapcalc to get a new layer from two complementary layers, the result
contains no data, whether interactively or  non-interactively.

GRASS:~ >r.mapcalc asp_cost=asp_north+asp_south

EXECUTING asp_cost = ...  100%
CREATING SUPPORT FILES FOR asp_cost
GRASS:~ >r.report asp_cost units=percent
...
...
|-----------------------------------------------------------------------------|
|                        Category Information                          |   %
|
|#|description                                                         | cover|
|-----------------------------------------------------------------------------|
|*|no data. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .|100.00|
|-----------------------------------------------------------------------------|
...
...
GRASS:~ >r.report asp_north units=percent
...
...
|-----------------------------------------------------------------------------|
|                        Category Information                          |   %
|
|#|description                                                         | cover|
|-----------------------------------------------------------------------------|
|1|0 thru 180 . . . . . . . . . . . . . . . . . . . . . . . . . . . . .| 51.35|
|*|no data. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .| 48.65|
|-----------------------------------------------------------------------------|
...
...
GRASS:~ >r.report asp_south units=percent
...
...
|-----------------------------------------------------------------------------|
|                        Category Information                          |   %
|
| #|description                                                        | cover|
|-----------------------------------------------------------------------------|
|10|181 thru 360 . . . . . . . . . . . . . . . . . . . . . . . . . . . | 45.34|
| *|no data. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . | 54.66|
|-----------------------------------------------------------------------------|
...
...

In fact, the problem also occurs with grass5 on my redhat 7.3 platform, which
I downloaded binaries just a few days ago from  a mirror site.
Forgive my poor English.

Thanks,

Zhao Jianwei
Tue, Oct 8 2002 06:05:52    Mail sent by guest  
This does not seem to be a bug and the tutorial probably was not written
for GRASS5 with null data. If the layers are complementary and use nulls,
then the result will be nulls. It is necessary to change the nulls
in the complemenary files to zeroes (e.g. using r.null) to get it right.
I suggest that the tutorial should get info attached to it that it may contain
material which is not valid for GRASS5

Helena
Tue, Oct 8 2002 09:47:18    Mail sent by mneteler  
Unfortunately we have no access to the document (we cannot distribute
it due to copyright limitations). The PROJECT ASSIST people do not
answer...

Markus
Tue, Oct 8 2002 09:47:20    Status changed to resolved by mneteler  
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