Matlab: Find given row in a matrix?

Gnovice's suggestion is even simpler than mine.

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I have a m-rows n-columns matrix in matlab, say M. I have a n-element row vector, i.e. An 1-row n-column matrix, say X.

I know X is a row somewhere in M. How can I find the index of M? Matlab link|improve this question asked Jun 2 '11 at 2:51Martin642111 69% accept rate.

EDIT: gnovice's suggestion is even simpler than mine: ~,indx=ismember(X,M,'rows') indx = 3 FIRST SOLUTION: You can easily do it using find and ismember. Here's an example: M=magic(4); %#your matrix M = 16 2 3 13 5 11 10 8 9 7 6 12 4 14 15 1 X=9 7 6 12; %#your row vector find(ismember(M,X),1) ans = 3.

2 You could modify your solution slightly using the 'rows' argument to ISMEMBER to remove the need for FIND: ~,index = ismember(X,M,'rows') – gnovice Jun 2 '11 at 3:19 @gnovice: thanks :) I've edited my solution. – Bring back spy Jun 2 '11 at 3:47.

This is a non-loop version. It is only suitable, if M (your matrix) is not very large, ie. N and m are small.

X is your row: function ind = findRow(M,X) tmp = M - repmat(X,size(M,1),1); ind = find(tmp,1); end If M is too large, it might be faster, to iterate the rows of M and compare every row with your vector. @Edit: renamed variables to match the names used in the question.

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