[Qgis-user] Logarithmic functions

[Alister Hood]

> Date: Wed, 15 Feb 2012 16:00:05 -0800 (PST)
> From: magerlin <MAP at ramboll.dk>
> Subject: [Qgis-user] Logarithmic functions
> To: qgis-user at lists.osgeo.org
> Message-ID: <1329350405948-4474344.post at n6.nabble.com>
> Content-Type: text/plain; charset=us-ascii
>
> 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.

I don't know about the Raster Calculator, but it seems the field calculator does not have log functions in QGIS 1.7.3
In QGIS master there is ln(), log(a,b) and log10().  But there seems to be a bug with log(a,b)...