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How can I make smaller matrices (size unknown) from a large matrix?

Asked by John Hunt on 3 Oct 2017
Latest activity Commented on by Cedric Wannaz
on 4 Oct 2017
I have a matrix that has 51 columns and 46999 rows. The 8th column has values 1 to 36. I want to create a matrix for each value in that column (36 total). I want to stack rows that have the same value to make these matrices.
Thus far I know can use a for loop to set up a matrix 36 times then I was trying to use a while loop to "stack" the rows that share the same value in the 8th column, but I can't get that while loop right. Any suggestions?

  1 Comment

That worked awesome! Thank you, could you explain it a bit so I can understand a bit better whats going on please?

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1 Answer

Answer by James Tursa
on 3 Oct 2017
 Accepted Answer

M = your matrix;
result = cellfun(@(x)M(M(:,8)==x,:),num2cell(1:36),'uni',false);

  8 Comments

I was just being fair, because if we are both roughly in the same timezone, it is getting late (!) and the probability that we implement extra calls to num2cell induced by an inadvertent use of cellfun is nearing the unit ;)
+1 for both of you.
@Cedric: Now you know the reason, why I "boost" sometimes. It is for the cases, where the standard voting system is to rough. :-)
:-)
It has already been proposed, but I really think that allowing voting for comment would help. This would lead people to add much more value to others' answers by taking time to write well developed comments.

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