title: Undefined function 'imgradientxy' for input arguments of type 'uint8'
body: <p>I'd like to call functions like <code>imgradientxy</code> or <code>gray2ind</code> in matlab, but either one will cause the error of <code>Undefined function 'imgradientxy' for input arguments of type 'uint8'.</code></p>
  
  <p>I'm using R2012a version and added <code>toolbox</code> to path.</p>
  
  <p>MATLAB Version: 7.14.0.739 (R2012a)</p>
  
  <p>Mapping Toolbox                                       Version 3.5        (R2012a)</p>
  
  <p><code>imgradientxy</code> and <code>gray2ind</code> are native functions of matlab. Why is that happening?</p>