how to find location of nans in a matrix

I have a very large matrix. I need to find locations of nans (not a number) in the matrix. for example if there exists a nan in row=2 and coloumn=5, It must give me the answer (2,5)

what do I have to do?

Answer 1

[Walter Roberson]

 [r, c] = find(isnan(YourMatrix)) ;

Answer 2

[Luca Ferro]

supposing you matrix is named 'm':

nan=isnan(m); %returns 1 where NaN

[rIdx,cIdx]=find(nan==1); %returns row and col indeces whre the 1 is

nanIdx=[rIdx(:),cIdx(:)]; %creates rows column pairs, every row represents a pair

%to access the pairs do:

nanIdx(1,:) %first pair (row-col where NaN is)

nanIdx(2,:) %second pair, and so on

[Stephen23]

It would be best not using variable name NAN and shadowing the inbuilt function of that name:

nan(1,2)

ans = 1×2

NaN NaN

Note that nan==1 converts a logical array to an exactly identical logical array, so that EQ is superfluous.