PSI(3)

SYNOPSIS
FUNCTION PSI (X)

NAME
psi - Compute the Psi (or Digamma) function.

LIBRARY
SLATEC (FNLIB)

CATEGORY
C7C

TYPE
SINGLE PRECISION (PSI-S, DPSI-D, CPSI-C)

KEYWORDS
DIGAMMA FUNCTION, FNLIB, PSI FUNCTION, SPECIAL FUNCTIONS

AUTHOR
Fullerton, W., (LANL)

DESCRIPTION
PSI(X) calculates the psi (or digamma) function for real argument X. PSI(X) is the logarithmic derivative of the gamma function of X. Series for PSI on the interval 0. to 1.00000D+00 with weighted error 2.03E-17 log weighted error 16.69 significant figures required 16.39 decimal places required 17.37 Series for APSI on the interval 0. to 2.50000D-01 with weighted error 5.54E-17 log weighted error 16.26 significant figures required 14.42 decimal places required 16.86

REFERENCES
(NONE)

ROUTINES CALLED
COT, CSEVL, INITS, R1MACH, XERMSG

REVISION HISTORY (YYMMDD)
770401 DATE WRITTEN
890531 Changed all specific intrinsics to generic. (WRB)
890531 REVISION DATE from Version 3.2
891214 Prologue converted to Version 4.0 format. (BAB)
900315 CALLs to XERROR changed to CALLs to XERMSG. (THJ)
900727 Added EXTERNAL statement. (WRB)
920618 Removed space from variable names. (RWC, WRB)