If isnan(x) make columns also NaN

I have a horizontal array or data 1:1505 made of Nans and 1s (inA4)

I also have a matrix of data 96:1505 (Approx4)

Where ever a NaN appears in 'inA1' I want the entire column of Approx 1 to become NaNs.

This is what I have come up with so far, but It's not working. I'm sure the solution is simple but I can not work it out thus far

      for i = 1:96;
          j = 1:1505;

         if inA4(j) == 1;
             Approx4(i,j) = Approx4(i,j);
         else isnan(Approx4(i,j));

         end;
      end;

Answer 1

[Stephen23]

This is trivial using basic MATLAB indexing:

>> A =  [1,2,3;4,5,6;7,8,9]
A =
   1   2   3
   4   5   6
   7   8   9
>> B = [1,NaN,1]
B =
     1   NaN     1
>> A(:,isnan(B)) = NaN
A =
     1   NaN     3
     4   NaN     6
     7   NaN     9

You should learn to how use MATLAB instead of fighting it with inefficient loops:

http://www.mathworks.com/matlabcentral/answers/228557-experts-of-matlab-how-did-you-learn-any-advice-for-beginner-intermediate-users

Answer 2

[Wolfgang]

 idxNaNs = isnan(inA4);    % find NaNs in inA4
 Approx4(:,idxNaNs) = NaN; % set columns to NaN