dlgamma - derivative of gammaln function, psi function

Calling Sequence

y = dlgamma(x)

Parameters

• x : real vector
• y : real vector with same size.

Description

dlgamma(x) evaluates, at all the elements of x the logarithmic derivative of the gamma function which corresponds also to the derivative of the gammaln function :

         d/dx (gamma(x)) / gamma(x) = d/dx (ln gamma(x))
     

x must be real. Also known as the psi function.

Examples

dlgamma(0.5)

 

See Also

gamma  gammaln  

Author

W. J. Cody (code from Netlib (specfun))