title: Octave operator -: automatic broadcasting operation applied
body: <p>In octave 3.6.2, I have a matrix <code>X=[1 2 3; 2 4 5; 2 6 5; 2 3 7; 3 6 8; 2 4 6; 3 6 8; 4 7 10]</code> and I want to calculate X-mean(X), which gives me:</p>
  
  <pre><code>octave:2&gt; X-mean(X)
  warning: operator -: automatic broadcasting operation applied
  ans =
  
    -1.37500  -2.75000  -3.50000
    -0.37500  -0.75000  -1.50000
    -0.37500   1.25000  -1.50000
    -0.37500  -1.75000   0.50000
     0.62500   1.25000   1.50000
    -0.37500  -0.75000  -0.50000
     0.62500   1.25000   1.50000
     1.62500   2.25000   3.50000
  </code></pre>
  
  <p>however, when I try the same command on a different machine, it complains that the sizes of matrices do not match:</p>
  
  <pre><code>error: operator -: nonconformant arguments (op1 is 7x3, op2 is 1x3)
  </code></pre>
  
  <p>Any idea how to activate that "<strong>automatic broadcasting operation</strong>" which is applied in the first case? (octave versions are the same!)</p>