[GRASS-user] Use of r.mode

GRASS GRASS user
1

Greetings

This new topic is related with

I need to calculate mode for a base map that is composed by float values.
r.mode base=base@PERMANENT cover=11073_B@PERMANENT output=saida

And I get:

ERROR: reading r.stats output
ERROR: No rules specified

This means that I’m not being able to apply this function just because my base map is a Float. Any ideas of how to fix this?

Thanks
Monica

2

Monica Buescu wrote:

Greetings

This new topic is related with

I need to calculate mode for a base map that is composed by float values.
r.mode base=base@PERMANENT cover=11073_B@PERMANENT output=saida
            
And I get:
ERROR: reading r.stats output
ERROR: No rules specified

This means that I'm not being able to apply this function just because my base map is a Float. Any ideas of how to fix this?

How about r.mapcalc base_integer=int(base) ?

The base map should be integer (category ) values, where the mode is calculated for all cells with the same cat value, so it indeed should be an integer raster.

Thanks
Monica

This mail was received via Mail-SeCure System.
------------------------------------------------------------------------

_______________________________________________
grass-user mailing list
grass-user@lists.osgeo.org
http://lists.osgeo.org/mailman/listinfo/grass-user

This mail was received via Mail-SeCure System.

3

Hi Mich
Thanks for the reply. I think it has worked but everytime I try to open, my winGRASS goes “bananas”.
Just to sum what I have done
1- Import a xyz ASCII file that is a float with a range of [166297.00 - 20855944.0] (not all values are used) and Rows: 4655 ;Columns: 4520 .
2- I did r.mapcalc int() to this file that gets the range of [166297 20855944].
QUESTION: can I apply int to a FLoat with values as big as this?
3- I did r.mode base=int_base coverage= 11073_B@PERMANENT (it’s a high-resolution image) output=output1

Ok it runs (it takes some time as expected)
Thern if I try to display it freezes… Even If I just try r.info output1 it also freezes.

Any thoughts aboutt this? (Thanks Micha)

On Tue, Oct 19, 2010 at 2:14 PM, Micha Silver <micha@arava.co.il> wrote:

Monica Buescu wrote:

Greetings

This new topic is related with

I need to calculate mode for a base map that is composed by float values.
r.mode base=base@PERMANENT cover=11073_B@PERMANENT output=saida
And I get:
ERROR: reading r.stats output
ERROR: No rules specified

This means that I’m not being able to apply this function just because my base map is a Float. Any ideas of how to fix this?

How about r.mapcalc base_integer=int(base) ?

The base map should be integer (category ) values, where the mode is calculated for all cells with the same cat value, so it indeed should be an integer raster.

Thanks
Monica

This mail was received via Mail-SeCure System.

grass-user mailing list
grass-user@lists.osgeo.org
http://lists.osgeo.org/mailman/listinfo/grass-user

This mail was received via Mail-SeCure System.

4

Hi Mich
Thanks for the reply. I think it has worked but everytime I try to open, my winGRASS goes “bananas”.

Hope you get some whipped cream with that :wink:

Just to sum what I have done
1- Import a xyz ASCII file that is a float with a range of [166297.00 - 20855944.0] (not all values are used) and Rows: 4655 ;Columns: 4520 .

About 20,000,000 cells. That should be OK.
Do you know how many different values are actually in the data?

2- I did r.mapcalc int() to this file that gets the range of [166297 20855944].
QUESTION: can I apply int to a FLoat with values as big as this?

An integer raster is represented by 32 bit signed integer values i.e. from (about) -2 billion to +2 billion. So you’re OK here.

3- I did r.mode base=int_base coverage= 11073_B@PERMANENT (it’s a high-resolution image) output=output1

Ok it runs (it takes some time as expected)
Thern if I try to display it freezes… Even If I just try r.info output1 it also freezes.

I’d try two things here. First can you change to a smaller region and rerun r.mode and try to display the results?
Second: the result of r.mode is a “reclass” of the original values. So I suppose it has to be recalculated each time you want to display. You can make that reclass map into a permanent raster by running:
r.mapcalc “output2 = output1”
Then try displaying the output2.

··· 
-- 
Micha Silver
Arava Development Co. +972-52-3665918
[http://www.surfaces.co.il](http://www.surfaces.co.il)
5

Hello

About 20,000,000 cells. That should be OK.
Do you know how many different values are actually in the data?

Yes… In this case is 6608. In other examples it can be 3000 or 2000. Why?

I’d try two things here. First can you change to a smaller region and rerun r.mode and try to display the results?

Yes. It worked with a much smaller image.

Second: the result of r.mode is a “reclass” of the original values. So I suppose it has to be recalculated each time you want to display. You can make that reclass map into a permanent raster by running:
r.mapcalc “output2 = output1”

I tried this and after 15 minutes running I gave up. Can this be related with memory restrictions?

Thanks Micha for your help
Micha

6

On 20/10/2010 12:18, Monica Buescu wrote:

Hello

About 20,000,000 cells. That should be OK.
Do you know how many different values are actually in the data?

Yes… In this case is 6608. In other examples it can be 3000 or 2000. Why?

Just to understand how complex the calculation of r.mode has to be.

I’d try two things here. First can you change to a smaller region and rerun r.mode and try to display the results?

Yes. It worked with a much smaller image.

Ah, good.

Second: the result of r.mode is a “reclass” of the original values. So I suppose it has to be recalculated each time you want to display. You can make that reclass map into a permanent raster by running:
r.mapcalc “output2 = output1”

I tried this and after 15 minutes running I gave up. Can this be related with memory restrictions?

Well, that’s not good. Yes, maybe a problem with disk space or memory? l’ll have to leave to someone more knowledgeable to answer here.
If you just let it run for longer will it finish?

7

Well, that’s not good. Yes, maybe a problem with disk space or memory? l’ll have to leave to someone more knowledgeable to answer here.

Thanks Micha
Probaby in this case is “Memory” space. Because for Smaller images I don’t get any problem and bigger images I’m getting this problem.
As anyone experienced such a problem? (GRASS takes toooooo long to display an image or apply r.mapcalc?

8

Hi there,
I have created a raster file from r.mode. It’s a big image (is true) and it might me heavy but I’m not being able to “get” r.info information… In a 4GB RAM memory machine I have r.info and after 9 minutes It didn’t printed anything. So I’m not being able to retrieve information from this raster. Any suggestion? Shall I create a copy of this file? and is this normal?

Thanks
Monica

On Thu, Oct 21, 2010 at 11:32 AM, Monica Buescu <monicabuescu1985@gmail.com> wrote:

Well, that’s not good. Yes, maybe a problem with disk space or memory? l’ll have to leave to someone more knowledgeable to answer here.

Thanks Micha
Probaby in this case is “Memory” space. Because for Smaller images I don’t get any problem and bigger images I’m getting this problem.
As anyone experienced such a problem? (GRASS takes toooooo long to display an image or apply r.mapcalc?