[BioC] function to find coodinates in an array

[lgautier at altern.org]

> Dear list,
>
> I am looking for a function/way to get the array coordinates of given
> elements in an array. What I mean is the following:
> - Let X be a 3D array
> - I find the ordering of the elements of X by ord <- order(X) (this
> returns me a vector)
> - I now want to find the x,y,z coordinates of each element of ord
>
> Can anyone help me?

...cross-posting is generally not advised. Identify where to post first
is generally considered good practice.

In case no one on R-help came with a solution, here
is something that appears working (in toy examples):

# the easy one first
Xx <- array(rep(seq(1, prod(dim(X)[1])), prod(dim(X)[c(2,3)])), dim(X))
# then making the other ones easy
Xy <- local({
             X <- aperm(X, c(2, 1, 3))
             Xy <- array(rep(seq(1, prod(dim(X)[1])), prod(dim(X)[c(2,3)])),
                         dim(X))
             aperm(Xy, c(2, 1, 3))
             })
Xz <- local({
             X <- aperm(X, c(3, 2, 1))
             Xz <- array(rep(seq(1, prod(dim(X)[1])), prod(dim(X)[c(2,3)])),
                         dim(X))
             aperm(Xz, c(3, 2, 1))
             })

# what you want:
Xx[ord]
Xy[ord]
Xz[ord]



L.




> Thanks!
>
> Ana
>
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