dpsi.f
DOUBLE PRECISION FUNCTION DPSI (X)
C***BEGIN PROLOGUE DPSI
C***PURPOSE Compute the Psi (or Digamma) function.
C***LIBRARY SLATEC (FNLIB)
C***CATEGORY C7C
C***TYPE DOUBLE PRECISION (PSI-S, DPSI-D, CPSI-C)
C***KEYWORDS DIGAMMA FUNCTION, FNLIB, PSI FUNCTION, SPECIAL FUNCTIONS
C***AUTHOR Fullerton, W., (LANL)
C***DESCRIPTION
C
C DPSI calculates the double precision Psi (or Digamma) function for
C double precision argument X. PSI(X) is the logarithmic derivative
C of the Gamma function of X.
C
C Series for PSI on the interval 0. to 1.00000E+00
C with weighted error 5.79E-32
C log weighted error 31.24
C significant figures required 30.93
C decimal places required 32.05
C
C
C Series for APSI on the interval 0. to 1.00000E-02
C with weighted error 7.75E-33
C log weighted error 32.11
C significant figures required 28.88
C decimal places required 32.71
C
C***REFERENCES (NONE)
C***ROUTINES CALLED D1MACH, DCOT, DCSEVL, INITDS, XERMSG
C***REVISION HISTORY (YYMMDD)
C 770601 DATE WRITTEN
C 890531 Changed all specific intrinsics to generic. (WRB)
C 890911 Removed unnecessary intrinsics. (WRB)
C 890911 REVISION DATE from Version 3.2
C 891214 Prologue converted to Version 4.0 format. (BAB)
C 900315 CALLs to XERROR changed to CALLs to XERMSG. (THJ)
C 900727 Added EXTERNAL statement. (WRB)
C 920618 Removed space from variable name. (RWC, WRB)
C***END PROLOGUE DPSI