finding max value from multidimensional array in R

Question

I have an array of dim 4x1x4x71x128. The first dim refers to 4 different models. The third dim refers to lower CI, Correlation, Upper CI and p-value.

What I need as output is a new array of dim 1x1x1x71x128 where the first dim refers to the max value of Correlation(3rd dim) among the 4 models(1st dim).

I tried the following:

newarray <- array(NA, c(1,1,1,71,128))
for (i in 1:4) {
  for (j in 1:nrow(array[1,1,1,,])) {
    for (k in 1:ncol(array[1,1,1,,])){
      newarray[i,1,1,j,k] <- max(array[i,1,1,j,k], na.rm = FALSE)
    }
  }
}

This returns me the maximum value not for Correlation but for lower CI. However, when I change operation to:

newarray[i,1,1,j,k] <- max(array[i,1,2,j,k], na.rm = FALSE)

It does not work. I believe I am not looping right but can't seem to figure it out.

Thanks for you help in advance!

It will help to have reproducible example with expected results - stackoverflow.com/questions/5963269/… — Bulat
– Bulat, Commented May 20, 2016 at 20:38
@nicola Unfortunately, the suggested code gives me NA values — nitimkc
– nitimkc, Commented May 20, 2016 at 22:05
@ Bulat I tried to reproduce an example with expected results: testarray <- array(sample(1:16), c(2,1,2,2,2)) resultarray <- array(c(12,14,13,7), c(1,1,1,2,2)) testarray[,1,2,,] # to compare results resultarray[1,1,1,,] # max value for each grid point — nitimkc
– nitimkc, Commented May 20, 2016 at 22:06

nitimkc · Accepted Answer · 2016-05-23 09:31:25Z

2

x.max <- apply(x , c(3,4,5) , 
                   function(x) 
                     ifelse(all(is.na(x)), NA, max(x, na.rm = TRUE)))

Solved! Result is of dim 4x71x128 with the 2nd element of 1st dim being the desired output.

answered May 23, 2016 at 9:31

nitimkc

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