Fwd: [Qgis-user] Logarithmic functions

[Agustin Lobo]

Morten,

As far as I know, the available functions are the ones with a key
only. For raster,
you can use another raster calculator provided by plugin Rastercalc,
outside the Raster tab in the
menu. You must install it from the GisLab repo,
http://gis-lab.info/programs/qgis/qgis-repo.xml
(I think you get it if you select Add Third party Repos)

If you need to do a lot of calculations, you probably want to use R, write
results through rgdal and display in QGIS. QGIS has a plugin to open R
from within
QGIS (Rmanager), but I'm not sure about its stability.
Another solution that I have not tried enough as to really advise it
might be using the python console.

Agus

El día 16 de febrero de 2012 01:00, magerlin <MAP at ramboll.dk> escribió:
> I am working with traffic noise and since the dB unit for measuring noise is
> logarithmic I often need the logarithmic function, but it does not seem to
> exist neither in field calculator nor in Raster Calculator?
>
> In Raster Calculater I can write log(xxx), but it just returns xxx. In field
> calculator I will get an error if I write log(xxx) or the like.
>
> -----
> Regards Morten
>
> Qgis 1.7.3 in Win7
> --
> View this message in context: http://osgeo-org.1560.n6.nabble.com/Logarithmic-functions-tp4474344p4474344.html
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