[GRASS-user] r.rescale - float instead of integer?

Johannes Radinger JRadinger at gmx.at
Wed Mar 23 04:16:49 EDT 2011

Am 23.03.2011 um 05:29 schrieb Glynn Clements:

> Johannes Radinger wrote:
>> I try to rescale a rastermap with category values ranging from 1 to 16.
>> I want to rescale them by dividing the values by the maximum value, like
>> 1 --> 1/16, 10-->10/16 and 16 --> 1). I tried to do that with the r.rescale tool with setting the output range to 0,1 like:
>> r.rescale input=input output=output to=0.0,1.0
>> but it I don't get float values as a results, only 0 and 1 as
>> integers. Does r.rescale handle floats
> No. r.rescale is a front-end to r.reclass, which only handles
> integers.
> r.recode provides similar functionality to r.reclass for
> floating-point data (but it creates an entirely new map; reclass maps
> only support integer data).
I looked at it but with r.code, I've to provide the input data range values as
fixed values (at least one) rather then saying use all values from min to max
as it is possible in rescale...

>> Or is there any other simple way to divide the single raster values
>> by the maximum value and get a float value as result?
> 	r.mapcalc "output = input / 16.0"

I think r.mapcalc is probably the best solution, but as I don't know the maximum
value in every case (I've to process several maps), I wanted to automatize.
Probably I've to write a script to read the max value and parse it to the mapcalc function.
My problem: First, I don't know how to do that, Second there is this python-script issue
on my mac (see other thread)...

> -- 
> Glynn Clements <glynn at gclements.plus.com>
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