# How to access certain matrix elements and turn into NaN?

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RG on 18 Aug 2016
Commented: RG on 18 Aug 2016
Hi,
I have two matrices z and interior as shown below:
z =[ 9.0000 17.6400 29.1600 43.5600 60.8400 81.0000;
6.7493 13.2287 21.8679 32.6668 45.6255 60.7440;
1.1230 2.2011 3.6386 5.4354 7.5916 10.1071;
-5.0650 -9.9274 -16.4105 -24.5145 -34.2393 -45.5848;
-8.7197 -17.0907 -28.2520 -42.2035 -58.9454 -78.4777;
-8.0134 -15.7062 -25.9633 -38.7846 -54.1703 -72.1202]
interior =[ 0 0 0 0 0 0;
0 0 0 0 0 0;
0 0 1 1 0 0;
0 0 1 1 0 0;
0 0 0 0 0 0;
0 0 0 0 0 0]
I am trying to extract the subscript indices of elements that are 1 in a matrix called interior and then turn the elements with same subscript indices (i.e [3.6386 5.4354; -16.4105 -24.5145]) into NaN in a matrix called z.
So far I have tried to extract the subscript indices as below:
[row,col] = find(interior)
combine = [row, col]
And I tried to use for loop to access the elements with same subscript indices in a matrix z, but couldn't work my way out. Could I get some help on this please? Sorry if it is a too simple question.

cbrysch on 18 Aug 2016
z(find(interior))=NaN;
should work. It is better to vectorize your data than using a loop.

#### 1 Comment

RG on 18 Aug 2016
Excellent!! That did the trick. Thanks a lot.