title: What causes "Jacobian matrix" to be singular in SAS?
body: <p>I have a simple SAS (version 9.2) program as follows,</p>
  
  <pre><code>proc model;
  cdf('normal',log(V/100)+1)=0.5;
  bounds V&gt;0;
  solve V/solveprint;
  run;
  </code></pre>
  
  <p>It throws exception that says jacobian matrix to be singular, </p>
  
  <pre><code>The Newton method Jacobian matrix of partial derivatives of the
  equations with respect to the variables to be solved is singular.
  </code></pre>
  
  <p>What is the possible cause of this error?</p>
  
  <p>Update: I have simplified the problem a bit. When modified to "cdf('normal', X)=0.5", it works without exception.</p>
  
  <p>Update2: bounds is updated to V>0; but exception still there</p>