title: Matlab reading 24-bit ascii-hex file into a 32-bit signed
body: <p>I'd like to plot every 9th element from an ascii file containg a single column of 24-bit signed hex values </p>
  
  <pre><code>ex.
  813457
  123456
  241566
  etc..
  </code></pre>
  
  <p>The problem is, I can't get Matlab to treat values 800000-FFFFFF as negative, presumably because it's not sign extending it into 32-bits. </p>
  
  <p>I thought of breaking it up into strings, then converting, but sscanf requires the '0x' to convert signed %i hex values so I'm forced to use unsigned:</p>
  
  <pre><code> C = textscan(fp, '%s')        %generates 16380x1 cell  (instead of normal array?!)
   sscanf (C{1,1}{1,1}, '%x')    %convert first ascii hex element from cell to unsigned hex
  </code></pre>
  
  <p>Interestingly, as a test, just doing hex2dec('FFC00000') results in a postive number, how can I force all the ascii lines in the file to be imported as an array of signed 24 or 32bit data?</p>