      SUBROUTINE LAMPPF(P,ALAMBA,PPF)
C
C     PURPOSE--THIS SUBROUTINE COMPUTES THE PERCENT POINT
C              FUNCTION VALUE FOR THE (TUKEY) LAMBDA DISTRIBUTION
C              WITH TAIL LENGTH PARAMETER VALUE = ALAMBA.
C              IN GENERAL, THE PROBABILITY DENSITY FUNCTION 
C              FOR THIS DISTRIBUTION IS NOT SIMPLE.
C              THE PERCENT POINT FUNCTION FOR THIS DISTRIBUTION IS
C              G(P) = ((P**ALAMBA)-((1-P)**ALAMBA))/ALAMBA
C              NOTE THAT THE PERCENT POINT FUNCTION OF A DISTRIBUTION 
C              IS IDENTICALLY THE SAME AS THE INVERSE CUMULATIVE
C              DISTRIBUTION FUNCTION OF THE DISTRIBUTION.
C     INPUT  ARGUMENTS--P      = THE SINGLE PRECISION VALUE 
C                                (BETWEEN 0.0 AND 1.0)
C                                AT WHICH THE PERCENT POINT 
C                                FUNCTION IS TO BE EVALUATED.
C                     --ALAMBA = THE SINGLE PRECISION VALUE OF LAMBDA 
C                                (THE TAIL LENGTH PARAMETER).
C     OUTPUT ARGUMENTS--PPF    = THE SINGLE PRECISION PERCENT
C                                POINT FUNCTION VALUE.
C     OUTPUT--THE SINGLE PRECISION PERCENT POINT
C             FUNCTION VALUE PPF FOR THE TUKEY LAMBDA DISTRIBUTION
C             WITH TAIL LENGTH PARAMETER = ALAMBA.
C     PRINTING--NONE UNLESS AN INPUT ARGUMENT ERROR CONDITION EXISTS. 
C     RESTRICTIONS--IF ALAMBA IS POSITIVE,
C                   THEN P SHOULD BE BETWEEN 0.0 AND 1.0, INCLUSIVELY.
C                   IF ALAMBA IS NON-POSITIVE,
C                   THEN P SHOULD BE BETWEEN 0.0 AND 1.0, EXCLUSIVELY.
C     OTHER DATAPAC   SUBROUTINES NEEDED--NONE.
C     FORTRAN LIBRARY SUBROUTINES NEEDED--ALOG.
C     MODE OF INTERNAL OPERATIONS--SINGLE PRECISION.
C     LANGUAGE--ANSI FORTRAN. 
C     REFERENCES--FILLIBEN, SIMPLE AND ROBUST LINEAR ESTIMATION
C                 OF THE LOCATION PARAMETER OF A SYMMETRIC
C                 DISTRIBUTION (UNPUBLISHED PH.D. DISSERTATION,
C                 PRINCETON UNIVERSITY), 1969, PAGES 21-44, 229-231,
C                 PAGES 53-58.
C               --FILLIBEN, 'THE PERCENT POINT FUNCTION',
C                 (UNPUBLISHED MANUSCRIPT), 1970, PAGES 28-31.
C               --HASTINGS, MOSTELLER, TUKEY, AND WINDSOR,
C                 'LOW MOMENTS FOR SMALL SAMPLES:  A COMPARATIVE
C                 STUDY OF ORDER STATISTICS', ANNALS OF
C                 MATHEMATICAL STATISTICS, 18, 1947,
C                 PAGES 413-426.
C     WRITTEN BY--JAMES J. FILLIBEN
C                 STATISTICAL ENGINEERING LABORATORY (205.03)
C                 NATIONAL BUREAU OF STANDARDS
C                 WASHINGTON, D. C. 20234
C                 PHONE:  301-921-2315
C     ORIGINAL VERSION--JUNE      1972. 
C     UPDATED         --SEPTEMBER 1975. 
C     UPDATED         --NOVEMBER  1975. 
C
C---------------------------------------------------------------------
C
      IPR=6
C
C     CHECK THE INPUT ARGUMENTS FOR ERRORS
C
      IF(ALAMBA.LE.0.0.AND.P.LE.0.0)GOTO50
      IF(ALAMBA.LE.0.0.AND.P.GE.1.0)GOTO50
      IF(ALAMBA.GT.0.0.AND.P.LT.0.0)GOTO50
      IF(ALAMBA.GT.0.0.AND.P.GT.1.0)GOTO50
      GOTO90
   50 WRITE(IPR,1)
      WRITE(IPR,46)P
      RETURN
   90 CONTINUE
    1 FORMAT(1H ,115H***** FATAL ERROR--THE FIRST  INPUT ARGUMENT TO THE
     1 LAMPPF SUBROUTINE IS OUTSIDE THE ALLOWABLE (0,1) INTERVAL *****)
   46 FORMAT(1H , 35H***** THE VALUE OF THE ARGUMENT IS ,E15.8,6H *****)
C
C-----START POINT-----------------------------------------------------
C
      IF(-0.001.LT.ALAMBA.AND.ALAMBA.LT.0.001)GOTO150
      GOTO250
  150 PPF=ALOG(P/(1.0-P))
      RETURN
C
  250 PPF= (P**ALAMBA-(1.0-P)**ALAMBA)/ALAMBA
      RETURN
C
      END 
