How do I get every combination of 3 vectors?
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Hello!
I have 3 vectors, one is a 35x1, one is a 31x1 and the last one is a 13x1. I want to create some kind of loop that outputs a number from the first, a number from the second, and a number from a third, over and over, eventually outputting every combination.
If I am not clear, please comment.
Thanks!
-Kevin
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Accepted Answer
Bruno Luong
on 2 Aug 2020
Edited: Bruno Luong
on 2 Aug 2020
yourvector1 = ...
yourvector2 = ...
yourvector3 = ...
Then
c = {yourvector1, yourvector2, yourvector3};
c = flip(c);
[c{:}] = ndgrid(c{:});
c = cellfun(@(x) x(:), flip(c), 'unif', 0);
c = cat(2, c{:});
check
disp(c)
3 Comments
Bruno Luong
on 2 Aug 2020
Edited: Bruno Luong
on 2 Aug 2020
c is an array of combination.
- Row dimension corresponds to different combination,
- Column dimension corresponds to yourvector1, yourvector2, yourvector3 values.
You have to tell us what you meant by "use one at the time", but it probably goes like this
for i=1:size(c,1)
combi = c(i,:); % 1 x 3 vector
% do something with it
...
end
You probably need more learning of basic stuff of MATLAB/programming.
More Answers (2)
Image Analyst
on 2 Aug 2020
Here's a for loop way to do it:
% Create 3 sample vectors, one is a 35x1, one is a 31x1 and the last one is a 13x1.
v1 = (1:35)'; % Actual values are whatever yours are - not a ramp like this.
v2 = (1:31)';
v3 = (1:13)';
% Get 3 random selection orderings:
order1 = randperm(length(v1));
order2 = randperm(length(v2));
order3 = randperm(length(v3));
% Now make 3 loops
for k1 = 1 : length(order1)
index1 = order1(k1);
for k2 = 1 : length(order2)
index2 = order2(k2);
for k3 = 1 : length(order3)
index3 = order3(k3);
fprintf('Processing index %d from v1, index %d from v2, and index %d from v3.\n', index1, index2, index3);
end
end
end
Of course you can do it with a built-in function rather than loops like Matt showed you.
6 Comments
Image Analyst
on 2 Aug 2020
You're welcome. Thanks for voting for it though. Matt's answer is the more MATLAB-y, vectorized way of doing it and is probably what I would have done. I just offered the looping way of doing it because that's what you specifically asked for, and sometimes the vectorized methods use functions, which, honestly, can be more confusing to beginners than a simple, intuitive for loop.
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