[R] Using apply on a three dimensional matrix and passing multiple arguments to user defined function

[Justin Peter]

Dear R-user,

I have a three-dimensional matrix of atmospheric data. The first two dimensions are spatial (lon and lat) and the third is time, such that

dim(data) <- c(nlon,nlat,ntime)

I wish to apply a land sea mask data which is a matrix of "0" and "1" if dim(nlon,nlat)

dim(lsmask) <- c(nlon,nlat)

I wish to set all of the elements in the two-dimensional array of data[,,ntime] for every 1:length(ntime).

I could do this in a loop:

for (i in 1:ntime){
    data[,,i][which(lsmask == 0)] <- NA
}

I would like to do this using apply, but I need to pass two variables to the function in apply (data and lsmask), where data is a two-dimensional array.

I tried:

mask <- function(x,y) {x[which(y==0)] <- NA}

masked_data <- apply(data,c(1,2),mask,y=lsmask)

but I get back a vector of dim(nlon,nlat) populated with NA.

Any clues as to what I am missing?

Thanks in advance for you help.

Kind regards,
Justin



--
Justin Peter
Research Fellow
International Centre for Applied Climate Sciences,
University of Southern Queensland
West St, Toowoomba, QLD, 4350
Australia

Email: justin.peter at usq.edu.au<mailto:justin.peter at usq.edu.au>
Ph: +61 (0) 7 4631 1181
Fax: +61 (0) 7 4631 5581
Mob: +61 (0)474 774 107




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