| What are the rules for automatic removal of singleton dimensions, and can I have a way of disabling them, please? [message #82553] |
Sun, 23 December 2012 15:01  |
tom.grydeland
Messages: 51
Registered: September 2012
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Member |
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Hello all,
I was trying to visualize subsections of a windowing function when this bit me.
I was creating piecewise results in an array res[ix, iy, ii, jj], where the partial results were sums up to some value in the final two indices
for ii = 0, Kx-1 do begin
for jj = 0, Ky-1 do begin
visualize, total(total(res[*,*,0:ii,0:jj], 4), 3)
endfor
endfor
but the problem is that IDL (arbitrarily, IMO) discards trailing singleton dimensions on my indexing, so that res[*,*,0:ii,0:jj] ends up as a two-dimensional array when both ii and jj are zero, and a three-dimensional index on subsequent cases of jj being zero, which again causes the calls to 'total' to fail. The innermost portion of these loops become extraordinarily messy if trying to fix this problem.
I've fixed my program by reordering the indices (to [ii, jj, ix, iy]), but I am still miffed that this should be necessary.
Similarly, when I concatenate arrays of dimensions [x, j] and [y, j], I expect a result with dimensions [x+y, j], even when j is equal to 1. I'm trying to write programs independent of the actual value of j, but these arbitrary removals of singleton dimensions make my task that much harder.
Is there a way to disable this stripping of singleton dimensions?
--Tom Grydeland
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