[R] operating on arrays of unknown dimensionality

Vadim Organovich vogranovich at jumptrading.com
Fri Aug 8 18:42:11 CEST 2008

Dear R-users,

I am looking for a way to assign to slices of arrays where dimensionality of the array is not a-priory known.

Specifically, I would like to be able to generalize the following example of dimensionality 2 to an arbitrary diminsionality:

In this example we create an array x, a smaller array y and then assign y to a slice of x.

> dimnmx <- list(c('a','b'), c('x','y','z')); x <- array(0, dim=sapply(dimnmx, length), dimnames=dimnmx)
> x
  x y z
a 0 0 0
b 0 0 0
> dimnmy <- list(c('a','b'), c('x','z')); y <- array(1, dim=sapply(dimnmy, length), dimnames=dimnmy)
> y
  x z
a 1 1
b 1 1
> x[dimnames(y)[[1]], dimnames(y)[[2]]] <- y
> x
  x y z
a 1 0 1
b 1 0 1

Now suppose I have an arbitrary lists dimnmx and dimnmy which are dimnames of respective arrays y and x. How do I assign y to the slice of x sliced out by dimnmy:

> dimnmx <- list(c('a','b'), c('x','y','z'), c('1','2')); x <- array(0, dim=sapply(dimnmx, length), dimnames=dimnmx)
> dimnmy <- list(c('a','b'), c('x','z'), c('2')); y <- array(1, dim=sapply(dimnmy, length), dimnames=dimnmy)
> something to the effect of do.call('[', list(x, dimnames(y))) <- y


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