<?xml version="1.0" encoding="ISO-8859-1" standalone="no"?>
<!DOCTYPE MAN SYSTEM "../../manrev.dtd">
<MAN>
  <LANGUAGE>eng</LANGUAGE>
  <TITLE>dlgamma</TITLE>
  <TYPE>Scilab Function</TYPE>
  <DATE>September 1997</DATE>
  <SHORT_DESCRIPTION name="dlgamma">  derivative  of gammaln function, psi function</SHORT_DESCRIPTION>
  <CALLING_SEQUENCE>
    <CALLING_SEQUENCE_ITEM> y = dlgamma(x)  </CALLING_SEQUENCE_ITEM>
  </CALLING_SEQUENCE>
  <PARAM>
    <PARAM_INDENT>
      <PARAM_ITEM>
        <PARAM_NAME>x</PARAM_NAME>
        <PARAM_DESCRIPTION>
          <SP>: real vector</SP>
        </PARAM_DESCRIPTION>
      </PARAM_ITEM>
      <PARAM_ITEM>
        <PARAM_NAME>y</PARAM_NAME>
        <PARAM_DESCRIPTION>
          <SP>: real vector with same size.</SP>
        </PARAM_DESCRIPTION>
      </PARAM_ITEM>
    </PARAM_INDENT>
  </PARAM>
  <DESCRIPTION>
    <P><VERB>dlgamma(x)</VERB> evaluates, at all the elements of <VERB>x</VERB> the logarithmic 
    derivative of the gamma function which corresponds also to the derivative of the
    gammaln function :</P>
    <VERBATIM>
<![CDATA[
         d/dx (gamma(x)) / gamma(x) = d/dx (ln gamma(x))
     ]]>
    </VERBATIM>
    <P><VERB>x</VERB> must be real. Also known as the psi function.</P>
  </DESCRIPTION>
  <EXAMPLE>
<![CDATA[
dlgamma(0.5)

 ]]>
  </EXAMPLE>
  <SEE_ALSO>
    <SEE_ALSO_ITEM>
      <LINK>gamma</LINK>
    </SEE_ALSO_ITEM>
    <SEE_ALSO_ITEM>
      <LINK>gammaln</LINK>
    </SEE_ALSO_ITEM>
  </SEE_ALSO>
  <AUTHOR>W. J. Cody (code from Netlib (specfun))</AUTHOR>
</MAN>
