# betai.f

          REAL FUNCTION BETAI (X, PIN, QIN)
    C***BEGIN PROLOGUE  BETAI
    C***PURPOSE  Calculate the incomplete Beta function.
    C***LIBRARY   SLATEC (FNLIB)
    C***CATEGORY  C7F
    C***TYPE      SINGLE PRECISION (BETAI-S, DBETAI-D)
    C***KEYWORDS  FNLIB, INCOMPLETE BETA FUNCTION, SPECIAL FUNCTIONS
    C***AUTHOR  Fullerton, W., (LANL)
    C***DESCRIPTION
    C
    C   BETAI calculates the REAL incomplete beta function.
    C
    C   The incomplete beta function ratio is the probability that a
    C   random variable from a beta distribution having parameters PIN and
    C   QIN will be less than or equal to X.
    C
    C     -- Input Arguments -- All arguments are REAL.
    C   X      upper limit of integration.  X must be in (0,1) inclusive.
    C   PIN    first beta distribution parameter.  PIN must be .GT. 0.0.
    C   QIN    second beta distribution parameter.  QIN must be .GT. 0.0.
    C
    C***REFERENCES  Nancy E. Bosten and E. L. Battiste, Remark on Algorithm
    C                 179, Communications of the ACM 17, 3 (March 1974),
    C                 pp. 156.
    C***ROUTINES CALLED  ALBETA, R1MACH, XERMSG
    C***REVISION HISTORY  (YYMMDD)
    C   770401  DATE WRITTEN
    C   890531  Changed all specific intrinsics to generic.  (WRB)
    C   890531  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   900326  Removed duplicate information from DESCRIPTION section.
    C           (WRB)
    C   920528  DESCRIPTION and REFERENCES sections revised.  (WRB)
    C***END PROLOGUE  BETAI