masking z values (extract or subset on a 3-d array)

Andy,

Maybe this is confusing because the data really ought to be in a dataframe
with factors coding for treatments?

Here's one solution:

foo[,'z',] <- sapply(foo[,'z',], function(x) max(c(x, 0)))

THK

On 5/26/06, Andy Bunn <abunn at whrc.org> wrote:

This is driving me nuts. I have a 3-D array that holds x,y,z
coordinates from multiple experiments. I need to clean the

data before

making it sp objects. I want to set all z-values < 0 to 0. In a 2-D
matrix this is trivial e.g., x[,x[1,]<0] <- 0. But I'm

stumped on how

to do this on a 3-D array without a loop. Given an array:

  foo <- array(rnorm(24), dim=c(4,3,2))
  dimnames(foo) <-

list(NULL,c('x','y','z'),c('Experiment1','Experiment2'))

  foo[,'z',]

How can I set foo[,'z',]<0 to 0?

a <- array(rnorm(64), c(4,4,4))
inds <- which(a < 0, arr.ind=TRUE)
a[inds] <- 0

Thanks, but I'm looking to set only the values from one dimension to zero.
As above, I just want to set the 'z' values to 0 if they are less than
one.
This works:

  foo <- array(rnorm(24), dim=c(4,3,2))
  dimnames(foo) <-list(NULL,c('x','y','z'),c('Experiment1','Experiment2'))
  foo[,'z',]
  #How can I set foo[,'z',]<0 to 0
  for(i in 1:2){
    foo[foo[,'z',i]<0,'z',i] = 0
  }
  foo

But it seems like one should be able to do this with apply or just '['.
I'm
at a loss.

-A

-- 
Timothy H. Keitt
http://www.keittlab.org/