[R] rbinom for a matrix

[Dylan Beaudette]

On Wednesday 09 July 2008, Ben Bolker wrote:
> 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 ...

Sorry about not including a reference to whom I was addressing. Meant that 
comment to go to the original poster.

-- 
Dylan Beaudette
Soil Resource Laboratory
http://casoilresource.lawr.ucdavis.edu/
University of California at Davis
530.754.7341