Dear all,

I have about 30,000 matrix (512x512), with values from 1 to N.
Each value on a matrix represent a habitat patch on my
matrix (i.e. my landscape). Non-habitat are stored as ZERO.
No I need to change each 1-to-N values for the same random
number.

Just supose my matrix is:
mymat<-matrix(c(1,1,1,0,0,0,0,0,0,0,0,
0,0,0,0,2,2,2,0,0,0,0,
0,0,0,0,2,2,2,0,0,0,0,
3,3,0,0,0,0,0,0,0,4,4,
3,3,0,0,0,0,0,0,0,0,0), nrow=5)

I would like that all cells with 1 come to be
runif(1,min=0.4, max=0.7), and cells with 2
be replace by another runif(...).

I can do it using for(), but it is very time expensive.
Any help are welcome.

cheers

milton

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