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Re: Generating a grid in the 3D,4D,5D...N space - Advice/Combinatory/Matrices [message #94873 is a reply to message #94871]

Tue, 14 November 2017 05:16

clement.feller@obspm. is currently offline

clement.feller@obspm.
Messages: 5
Registered: March 2017

Junior Member

Hello again,

Thanks both of you for your replies.

@Mike: I had looked into this before (I think Jeremy Bailin has published a code similar to yours called combigen.pro), but I then meet difficulties in selecting part of the generated combinations.

@Markus: I say, your code is sleek and nifty. I like your solution.

In the meantime, I had given this problem some more thoughts and I had come up with another slow ugly one that doesn't work for all cases:

function gen_indices_comb, m, n
;d I/O:
;d m -> long integer corresponds to the number of row in original table
;d n -> long integer corresponds to the number of columns in original table
;d
;d vals -> long array listing the vectors of indices to extract the
;d different possible combinations from the values of the original
;d table
;d
;d NOTES: SLOW CODE, a mitigation of the values of m and n is REQUIRED
;d Cases, where m & n are greater than 9, are not to considered
;d with this code

nmax = m^n

;c Assemble command generating vector of indices
cmd = 'tmp = ['
for ijk=(m-1L),1L,-1L do $
cmd += ' (lmn/n^'+string(ijk,format='(I03)')+') mod n,'
cmd += 'lmn mod n ]'

;c initialiase memory
ini = indgen(m,n)
tmp = lonarr(m)
val = lonarr(m, m^n)

;c execute command for each type of combination
for lmn=0L,(n^m-1L) do begin
void = execute(cmd)
if void ne 1 then message, ' > Error generating indices.'
val[*,ijk] = ini+tmp*m
endfor

return, val
end

Afn I'm considering this post solved, I'll update it with a definitive version of my solution.

Again thanks your replies,
/C

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[Message index]

		Generating a grid in the 3D,4D,5D...N space - Advice/Combinatory/Matrices By: clement.feller@obspm. on Mon, 13 November 2017 06:50
		Re: Generating a grid in the 3D,4D,5D...N space - Advice/Combinatory/Matrices By: Michael Galloy on Mon, 13 November 2017 16:04
		Re: Generating a grid in the 3D,4D,5D...N space - Advice/Combinatory/Matrices By: Markus Schmassmann on Tue, 14 November 2017 02:38
		Re: Generating a grid in the 3D,4D,5D...N space - Advice/Combinatory/Matrices By: Markus Schmassmann on Tue, 14 November 2017 03:29
		Re: Generating a grid in the 3D,4D,5D...N space - Advice/Combinatory/Matrices By: clement.feller@obspm. on Tue, 14 November 2017 05:16
		Re: Generating a grid in the 3D,4D,5D...N space - Advice/Combinatory/Matrices By: Dick Jackson on Tue, 14 November 2017 10:13
		Re: Generating a grid in the 3D,4D,5D...N space - Advice/Combinatory/Matrices By: clement.feller@obspm. on Fri, 24 November 2017 07:06

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