…but not really. Reading the docstring more carefully:
Transform the given dimensions of array A using function f. f is called on each slice of A of the form A[…,:,…,:,…]. dims is an integer vector specifying where the colons go in this expression. The results are concatenated along the remaining dimensions. For example, if dims is [1,2] and A is 4-dimensional, f is called on A[:,:,i,j] for all i and j. What I want to do, is rather call f on A[:,:,1,:] and A[:,:,end,:], but nothing in between 1 and end for that dimension. mapslices still eventually visit the entire array (either by slicing, or by iteration), but I only want to visit the “edges”. I might be missing something, though. // T On Thursday, March 24, 2016 at 1:48:36 AM UTC+1, Tomas Lycken wrote: Yes, probably - thanks for the tip! I'll see if I can cook something up... > > On Thursday, March 24, 2016 at 1:45:32 AM UTC+1, Benjamin Deonovic wrote: >> >> Can mapslices help here? >> >> >> On Wednesday, March 23, 2016 at 6:59:59 PM UTC-5, Tomas Lycken wrote: >>> >>> Is there an effective pattern to iterate over the “endpoints” of an >>> array along a given dimension? >>> >>> What I eventually want to accomplish is to apply a function (in this >>> case an equality test) to the two end points along a particular dimension >>> of an array. I think the pattern is easiest explained by considering 1D, 2D >>> and 3D: >>> >>> # assume the existence of some scalar-valued function f(x,y) >>> >>> A1 = rand(10) >>> f(A1[1], A1[end]) # d == 1 (the only possible value) -> one evaluation >>> >>> A2 = rand(10, 15) >>> map(f, A2[1,:], A2[end,:]) # d == 1 -> 15 evaluations >>> map(f, A2[:,1], A2[:,end]) # d == 2 -> 10 evaluations >>> >>> A3 = rand(10, 15, 8) >>> map(f, A3[1,:,:], A3[end,:,:]) # d == 1 -> 15x8 evaluations >>> map(f, A3[:,1,:], A3[:,end,:]) # d == 2 -> 10x8 evaluations >>> map(f, A3[:,:,1], A3[:,:,end]) # d == 3 -> 10x15 evaluations >>> >>> I just want to consider one dimension at a time, so given A and d, and >>> in this specific use case I don’t need to collect the results, so a >>> for-loop without an allocated place for the answer instead of a map is >>> just fine (probably preferrable, but it’s easier to go in that direction >>> than in the other). What I’m struggling with, is how to generally formulate >>> the indexing expressions (like [<d-1 instances of :>, 1, <size(A,d)-d >>> instances of :>], but not in pseudo-code…). I assume this can be done >>> somehow using CartesianIndexes and/or CartesianRanges, but I can’t get >>> my mind around to how. Any help is much appreciated. >>> >>> // T >>> >>> >>
