merge multi-dimensional arrays

Question

I have a list of arrays in which each array has only 2 elements with numbers and otherwise NA. There is only 1 number for any given element in all the arrays combined.

here is some example data.

ar1=array(NA,dim=c(2,3,4))
ar1[1,1,1]=100
ar2=array(NA,dim=c(2,3,4))
ar2[2,3,4]=200
ar3=array(NA,dim=c(2,3,4))
ar3[2,1,4]=300
ar=list(ar1,ar2,ar3)

Thanks!

Answer 1

pmax has an na.rm argument and you can pass ar as a list along with that argument to pmax with do.call:

> do.call(pmax, c(ar,  na.rm=TRUE) )
, , 1

     [,1] [,2] [,3]
[1,]  100   NA   NA
[2,]   NA   NA   NA

, , 2

     [,1] [,2] [,3]
[1,]   NA   NA   NA
[2,]   NA   NA   NA

, , 3

     [,1] [,2] [,3]
[1,]   NA   NA   NA
[2,]   NA   NA   NA

, , 4

     [,1] [,2] [,3]
[1,]   NA   NA   NA
[2,]  300   NA  200

Answer 2

You could use Reduce with any vectorized function that ignores NAs:

Reduce(function(x, y) ifelse(!is.na(x), x, y), ar)

Another example:

library(functional)
Reduce(Curry(pmax, na.rm = TRUE), ar)