      SUBROUTINE PROPOR(X,N,XMIN,XMAX,IWRITE,XPROP)
C
C     PURPOSE--THIS SUBROUTINE COMPUTES THE
C              THE SAMPLE PROPORTION WHICH IS THE 
C              PROPORTION OF DATA BETWEEN XMIN AND XMAX (INCLUSIVELY) 
C              IN THE INPUT VECTOR X.
C              THE SAMPLE PROPORTION = (THE NUMBER OF OBSERVATIONS
C              IN THE SAMPLE BETWEEN XMIN AND XMAX, INCLUSIVELY) / N. 
C              THE SAMPLE PROPORTION WILL BE A SINGLE PRECISION
C              VALUE BETWEEN 0.0 AND 1.0 (INCLUSIVELY).
C     INPUT  ARGUMENTS--X      = THE SINGLE PRECISION VECTOR OF
C                                (UNSORTED OR SORTED) OBSERVATIONS.
C                     --N      = THE INTEGER NUMBER OF OBSERVATIONS
C                                IN THE VECTOR X. 
C                     --XMIN   = THE SINGLE PRECISION VALUE 
C                                WHICH DEFINES THE LOWER LIMIT
C                                (INCLUSIVELY) OF THE REGION
C                                OF INTEREST.
C                     --XMAX   = THE SINGLE PRECISION VALUE 
C                                WHICH DEFINES THE UPPER LIMIT
C                                (INCLUSIVELY) OF THE REGION
C                                OF INTEREST.
C                     --IWRITE = AN INTEGER FLAG CODE WHICH 
C                                (IF SET TO 0) WILL SUPPRESS
C                                THE PRINTING OF THE
C                                SAMPLE PROPORTION
C                                AS IT IS COMPUTED;
C                                OR (IF SET TO SOME INTEGER 
C                                VALUE NOT EQUAL TO 0),
C                                LIKE, SAY, 1) WILL CAUSE
C                                THE PRINTING OF THE
C                                SAMPLE PROPORTION
C                                AT THE TIME IT IS COMPUTED.
C     OUTPUT ARGUMENTS--XPROP  = THE SINGLE PRECISION VALUE OF THE
C                                COMPUTED SAMPLE PROPORTION.
C                                THIS WILL BE A VALUE BETWEEN
C                                0.0 AND 1.0 (INCLUSIVELY). 
C     OUTPUT--THE COMPUTED SINGLE PRECISION VALUE OF THE
C             SAMPLE PROPORTION.
C     PRINTING--NONE, UNLESS IWRITE HAS BEEN SET TO A NON-ZERO
C               INTEGER, OR UNLESS AN INPUT ARGUMENT ERROR
C               CONDITION EXISTS.
C     RESTRICTIONS--THERE IS NO RESTRICTION ON THE MAXIMUM VALUE
C                   OF N FOR THIS SUBROUTINE.
C     OTHER DATAPAC   SUBROUTINES NEEDED--NONE.
C     FORTRAN LIBRARY SUBROUTINES NEEDED--NONE.
C     MODE OF INTERNAL OPERATIONS--SINGLE PRECISION.
C     LANGUAGE--ANSI FORTRAN. 
C     REFERENCES--SNEDECOR AND COCHRAN, STATISTICAL METHODS,
C                 EDITION 6, 1967, PAGES 207-213. 
C               --DIXON AND MASSEY, INTRODUCTION TO STATISTICAL
C                 ANALYSIS, EDITION 2, 1957, PAGES 81-82, 228-231.
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      1974. 
C     UPDATED         --SEPTEMBER 1975. 
C     UPDATED         --NOVEMBER  1975. 
C
C---------------------------------------------------------------------
C
      DIMENSION X(1)
C
      IPR=6
C
C     CHECK THE INPUT ARGUMENTS FOR ERRORS
C
      IF(N.LT.1)GOTO50
      IF(N.EQ.1)GOTO55
      IF(XMIN.EQ.XMAX)GOTO80
      HOLD=X(1)
      DO60I=2,N
      IF(X(I).NE.HOLD)GOTO90
   60 CONTINUE
      WRITE(IPR, 9)HOLD
      XPROP=0.0
      RETURN
   50 WRITE(IPR,15) 
      WRITE(IPR,47)N
      RETURN
   55 WRITE(IPR,18) 
      XPROP=0.0
      RETURN
   80 WRITE(IPR,26) 
      WRITE(IPR,49)XMIN
      XPROP=0.0
      RETURN
   90 CONTINUE
    9 FORMAT(1H ,108H***** NON-FATAL DIAGNOSTIC--THE FIRST  INPUT ARGUME
     1NT (A VECTOR) TO THE PROPOR SUBROUTINE HAS ALL ELEMENTS = ,E15.8,6
     1H *****)
   15 FORMAT(1H , 91H***** FATAL ERROR--THE SECOND INPUT ARGUMENT TO THE
     1 PROPOR SUBROUTINE IS NON-POSITIVE *****)
   18 FORMAT(1H ,100H***** NON-FATAL DIAGNOSTIC--THE SECOND INPUT ARGUME
     1NT TO THE PROPOR SUBROUTINE HAS THE VALUE 1 *****)
   26 FORMAT(1H ,46H***** FATAL ERROR--THE THIRD AND FOURTH INPUT ,
     1 48HARGUMENTS TO THE PROPOR SUBROUTINE ARE IDENTICAL) 
   47 FORMAT(1H , 35H***** THE VALUE OF THE ARGUMENT IS ,I8   ,6H *****)
   49 FORMAT(1H , 37H***** THE VALUE OF THE ARGUMENTS ARE ,E15.7   ,6H *
     1****)
C
C-----START POINT-----------------------------------------------------
C
      AN=N
      XPROP=0.0
      ISUM=0
      DO100I=1,N
      IF(X(I).LT.XMIN.OR.XMAX.LT.X(I))GOTO100
      ISUM=ISUM+1
  100 CONTINUE
      SUM=ISUM
      XPROP=SUM/AN
C
  101 IF(IWRITE.EQ.0)RETURN
      WRITE(IPR,999)
      WRITE(IPR,105)N,XMIN,XMAX,XPROP
  105 FORMAT(1H ,22HTHE PROPORTION OF THE ,I6,30H OBSERVATIONS IN THE IN
     1TERVAL ,E15.7,4H TO ,E15.7,4H IS ,E15.7)
  999 FORMAT(1H )
      RETURN
      END 
