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