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How to find every combination of values in a cell array?

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asobrado
asobrado on 7 May 2021
Edited: Stephan on 10 May 2021
Hi, I have a cell array with a variable number of values inside each cell, something like this:
M=
{1,2,3} {4,5,6}{7,8,9}
{10,11}{12,13}{14,15}
{16,17,18,19,20}{21,22,23,24}{25,26,27,28}
I want to create every possible combination of cell arrays contanining one value of each cell, something like this:
m1= m2= m3= m4=
{1}{4}{7} | {2}{4}{7} | {3}{4}{7} | {1}{5}{7}
{10}{12}{14} | {10}{12}{14} | {10}{12}{14} | {10}{12}{14}
{16}{21}{25} | {16}{21}{25} | {16}{21}{25} | {16}{21}{25}
---
and so on.
Is it possible to do it? Tried with nchoosek and cell2mat, but the vary in length of array is a problem I couldn't resolve.

Accepted Answer

Stephan
Stephan on 7 May 2021
Edited: Stephan on 10 May 2021
One way, using allcomb:
M = {[1,2,3], [4,5,6],[7,8,9];
[10,11],[12,13],[14,15];
[16,17,18,19,20],[21,22,23,24],[25,26,27,28]};
res = {allcomb(M{1,1:3}, M{2,1:3}, M{3,1:3})};
res = permute(reshape(res{:}',3,3,[]),[2 1 3]);
The order of the results is a bit different then you wanted, but always only one value is changed:
>> res(:,:,1:5)
ans(:,:,1) =
1 4 7
10 12 14
16 21 25
ans(:,:,2) =
1 4 7
10 12 14
16 21 26
ans(:,:,3) =
1 4 7
10 12 14
16 21 27
ans(:,:,4) =
1 4 7
10 12 14
16 21 28
ans(:,:,5) =
1 4 7
10 12 14
16 22 25
  1 Comment
asobrado
asobrado on 7 May 2021
Works perfect! It's quite a pity Matlab can't handle the size of the real cell array I am using, but the solution is very straightforward. Thank you.

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