title: Why is my logical mask not working on a 2D matrix in matlab properly?
body: <pre><code>X(100,371) 
  %% contains 100 datapoints for 371 variables
  </code></pre>
  
  <p>I want to keep only the data which are within mean+standard deviation:mean-standard deviation.</p>
  
  <p>This is how I am proceeding:</p>
  
  <pre><code>mx=mean(X);sx=std(X);      
  %%generate mean, std 
  %%this generates mx(1,371) and sx(1,371)
  
  mx=double(repmat(mx,100,1));
  %%this fills a matrix with the same datapoints, 
  %%100 times
  sx=double(repmat(sx,100,1));
  %% this gives mx(100,371) and sx(100,371)
  
  
  g=X&gt;mx-sx &amp; X&lt;mx+sx;        
  %%this creates a logical mask g(100,371)
  %%filled with 1s and 0s 
  
  test(g)=X(g);               
  %%this should give me test(100,371), but I get 
  %%test(37100), which is wrong as it doesnt maintain 
  %%the shape of X
  
  test=reshape(test,100,371)  
  %% but when I compare this to the my original matrix
  %% X(100,371) I hardly see a difference (datapoints 
  %% in test are still outside the range I want.
  </code></pre>
  
  <p>What am I doing wrong?</p>