title: coldfusion IRR calculation
body: <p>I am trying to replicate the IRR (internal rate of return) function in excel. I found one cfc in riaforge.com but it doesn't return the same value as the excel's irr. </p>
  
  <p>The newton - raphson method uses derivatives and I am not sure how to calculate derivatives in coldfusion.</p>
  
  <pre><code>year    cash flow
  ----    --------
  0       -4000
  1       1200
  2       1410
  3       1875
  4       1050 
  </code></pre>
  
  <p>should return 14.3% ( from wikipedia's example ) </p>
  
  <p>Has anybody done this before? 
  thanks</p>