Odd output from ind2sub

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Kate
Kate on 23 Jul 2014
Commented: Kate on 23 Jul 2014
I'm trying to spit out indices for max values in a large matrix at a specific point in time (in this case obs 1560, t(:, :, 1560))
>> [I J]=ind2sub(size(t), (max(max(t(:, :, 1560)))))
But my I is equal to the actual value in the cell, not the row
I =
28.5048
And J makes no sense:
J =
1
Is the error in my code obvious to anyone? Thanks,

Accepted Answer

Andrei Bobrov
Andrei Bobrov on 23 Jul 2014
Edited: Andrei Bobrov on 23 Jul 2014
s = size(t);
[val,ij] = max(reshape(t(:, :, 1560),[],1);
[ii,jj] = ind2sub(s(1:2),ij);
idxs = [ii,jj,1560];
or
ind = prod(s(1:2))*1559 + ij;
  1 Comment
Kate
Kate on 23 Jul 2014
Thanks Andrei, reshape was the addition that I needed.

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More Answers (1)

dpb
dpb on 23 Jul 2014
(max(max(t(:, :, 1560))))
is a single value for the maximum of the values of the requested plane. Thus there isn't any actual location to be converted from being returned.
If you write
[i,j]=ind2sub(size(t), find(max(max(t(:, :, 1560)))))
instead, you'll always get [1,1] because the result of the double max() operation is scalar.

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