[GRASS-user] Use of r.mode

Micha Silver micha at arava.co.il
Tue Oct 19 13:52:09 EDT 2010

On 10/19/2010 04:03 PM, Monica Buescu wrote:
> 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 ;-)

> 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 at 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 
> <http://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.

> Any thoughts aboutt this? (Thanks Micha)
> On Tue, Oct 19, 2010 at 2:14 PM, Micha Silver <micha at arava.co.il 
> <mailto:micha at 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 at PERMANENT cover=11073_B at 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
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Micha Silver
Arava Development Co. +972-52-3665918

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