[R-sig-Geo] Calculations with images

[adrian at maths.uwa.edu.au]

Agustin Lobo <Agustin.Lobo at ija.csic.es> writes:

> ai <- as.im(a)
> ai$v[ai$v==0]<-NA #0 values in the raster are the background
> adist <- distmap(as.owin(ai))
> adistlog <- adist
> adistlog$v <- log(adistlog$v+1) #log transform

In spatstat you can also use 'solutionset' to find the pixels that satisfy
a logical statement, and `eval.im' to do calculations with pixel values.
The code above is equivalent to

   ai <- as.im(a)
   aw <- solutionset(ai != 0)
   adist <- distmap(aw)
   adistlog <- eval.im(log(adist)+1)

Adrian Baddeley