[Qgis-user] mathematical functions in raster calculator

[Carlos Cerdán]

Hi Sergio:

Interesting question.

You can create a raster layer with a fix value per cell, then make the
function you want. For example, in raster calculator:

1. *("GDD at 1">0 or "GDD at 1"=<0)*2* gets a raster layer with value 2 per cell
(let's put name =value2).

2. *"value2"^"GDD at 1"* must be a layer with each cell elevated to some value
on "GDD at 1". If value in cell of "GDD at 1" is big, you get "inf" (infinite?)
values

Good luck

Carlos Cerdán


2013/10/16 Sergio A Estay <sergio.estay at uach.cl>

> Dear All,
>
> I am wondering if it is possible to use, in the raster calculator,
> different mathematical functions in that the defined in the raster calc GUI.
>
> By example, using my layer GDD (just positive values) I try this:
>
> exp("GDD at 1") but I obtained just NaN values in the result layer, the same
> with e^"GDD at 1"
>
>
> Also, if I try something like this:
>
> "GDD at 1"^2 , this worked perfect, but if I try:
>
> 2^"GDD at 1" this produced just NaN
>
> Any suggestions will be useful
>
> --
> Sergio A. Estay
> Inst. Ciencias Ambientales y Evolutivas
> Universidad Austral de Chile
> Casilla 567, Valdivia, Chile
> Phone: 5663-293913
> http://www.ciencias.uach.cl/**instituto/ciencias_**ambientales_evolutivas/
> **academicos/sergio-estay.php<http://www.ciencias.uach.cl/instituto/ciencias_ambientales_evolutivas/academicos/sergio-estay.php>
>
>
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