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SUBROUTINE BDTR

PURPOSE
   COMPUTES P(X) = PROBABILITY THAT THE RANDOM VARIABLE U,
   DISTRIBUTED ACCORDING TO THE BETA DISTRIBUTION WITH
   PARAMETERS A AND B, IS LESS THAN OR EQUAL TO X.  F(A,B,X),
   THE ORDINATE OF THE BETA DENSITY AT X, IS ALSO COMPUTED.

USAGE
   CALL BDTR(X,A,B,P,D,IER)

DESCRIPTION OF PARAMETERS
   X   - INPUT SCALAR FOR WHICH P(X) IS COMPUTED.
   A   - BETA DISTRIBUTION PARAMETER (CONTINUOUS).
   B   - BETA DISTRIBUTION PARAMETER (CONTINUOUS).
   P   - OUTPUT PROBABILITY.
   D   - OUTPUT DENSITY.
   IER - RESULTANT ERROR CODE WHERE
       IER= 0 --- NO ERROR
       IER=-1,+1  CDTR HAS BEEN CALLED AND AN ERROR HAS
		  OCCURRED.  SEE CDTR.
       IER=-2 --- AN INPUT PARAMETER IS INVALID.  X IS LESS
		  THAN 0.0 OR GREATER THAN 1.0, OR EITHER A OR
		  B IS LESS THAN 0.5 OR GREATER THAN 10**(+5).
		  P AND D ARE SET TO -1.E75.
       IER=+2 --- INVALID OUTPUT.  P IS LESS THAN ZERO OR
		  GREATER THAN ONE.  P IS SET TO 1.E75.

REMARKS
   SEE MATHEMATICAL DESCRIPTION.

SUBROUTINES AND FUNCTION SUBPROGRAMS REQUIRED
   DLGAM
   NDTR
   CDTR

METHOD
   REFER TO R.E. BARGMANN AND S.P. GHOSH, STATISTICAL
   DISTRIBUTION PROGRAMS FOR A COMPUTER LANGUAGE,
   IBM RESEARCH REPORT RC-1094, 1963.