Polygamma Function
Function:
double
gsl_sf_psi_n
(int
m
, double
x
)
Function:
int
gsl_sf_psi_n_e
(int
m
, double
x
, gsl_sf_result *
result
)
These routines compute the polygamma function \psi^{(m)}(x) for m >= 0, x > 0.