[R] function to find coodinates in an array

Martin Maechler maechler at stat.math.ethz.ch
Fri Aug 17 08:59:37 CEST 2007

>>>>> "GaGr" == Gabor Grothendieck <ggrothendieck at gmail.com>
>>>>>     on Thu, 16 Aug 2007 23:46:28 -0400 writes:

    GaGr> Get the indices using expand.grid and then reorder
    GaGr> them: set.seed(1); X <- array(rnorm(24), 2:4) # input
    GaGr> X # look at X

    GaGr> do.call(expand.grid, sapply(dim(X), seq))[order(X),]

Excellent, Gabor!

Definitely the nicest of the solutions so far!

    GaGr> On 8/16/07, Ana Conesa <aconesa at ochoa.fib.es> wrote:
    >> 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?
    >> Thanks!
    >> Ana

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