[R] rbinom for a matrix
Ben Bolker
bolker at ufl.edu
Wed Jul 9 21:59:21 CEST 2008
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Dylan Beaudette wrote:
 On Wednesday 09 July 2008, Ben Bolker wrote:
> ACroske <Audy3272 <at> yahoo.com> writes:
>> I have a large matrix full of probabilities; I would like to convert
each
>> probability to a 1 or a 0 using rbinom.
>> How can I do this on the entire matrix? The matrix was converted from a
>> raster ArcMap dataset, so the matrix is essentially a map. Because of
>> this, I have no column headings.
>> Thanks!
> How about
>
> matrix(rbinom(length(m),prob=m,size=1),nrow=nrow(m))
>
> or (perhaps marginally more efficiently?)
>
> y < (runif(m)<m)
> storage.mode(y) < "double"
>
> Ben Bolker
>

 Wait a second. Are you trying to convert each probability into the most
 likely '1' or '0' through rounding? The code example above will give
you a
 different answer every time you run it. Is that what you are looking for?

 Just curious,

 Dylan

~ I assumed that since the original poster said "convert each
probability to a 1 or 0 using rbinom" that they did indeed want
a random assignment, rather than rounding ...
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