SUBROUTINE BOXES(MM, M, N, A, CLAB, RLAB, TITLE, XMIN, XMAX, NC,
     *                 IVAR, IERR, OUNIT)
C
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C
C   PURPOSE
C   -------
C
C      PRODUCES A PLOT IN THE FORM OF A 3-DIMENSIONAL BOX OF THREE
C      OR MORE VARIABLES FOR EACH CASE.
C
C   DESCRIPTION
C   -----------
C
C   1.  THE ORIGIN OF THE COORDINATE SYSTEM IS THE LOWER RIGHT CORNER
C       OF EACH BOX.  THE VARIABLES APPEAR IN THE ORDER THEY ARE PLACED
C       IN THE IVAR ARRAY.  FOR EXAMPLE, THE FIRST VARIABLE IN THE
C       X-DIRECTION WILL BE THE (1,1) ELEMENT OF THE ARRAY IVAR AND
C       WILL BE REPRESENTED ON THE BOX AS STARTING AT THE ORIGIN MOVING
C       TO THE LEFT UNTIL THE FIRST DIVIDER.  THE SECOND VARIABLE WILL
C       BE THE (1,2) ELEMENT OF THE ARRAY IVAR AND WILL BE REPRESENTED
C       ON THE BOX AS STARTING AT THE FIRST DIVIDER AND MOVE LEFT UNTIL
C       THE NEXT DIVIDER, ETC.  THE FIRST VARIABLE IN THE Y-DIRECTION
C       WILL BE THE (2,1) ELEMENT OF IVAR AND WILL BE REPRESENTED ON
C       THE BOX AS STARTING AT THE ORIGIN AND MOVING VERTICALLY UNTIL
C       THE FIRST DIVISION.  THE FIRST VARIABLE IN THE Z-DIRECTION IS
C       THE (3,1) ELEMENT OF IVAR AND WILL BE REPRESENTED ON THE BOX AS
C       STARTING AT THE ORIGIN AND MOVING IN A DIAGONAL DIRECTION UNTIL
C       THE FIRST DIVISION.  THE BOXES ARE DRAWN ON FORTRAN UNIT OUNIT.
C
C       FOR EXAMPLE, IF VARIABLES 1 AND 2 ARE TO BE PLOTTED ON THE
C       X-AXIS, VARIABLES 3 AND 4 ON THE Y-AXIS, AND VARIABLE 5 ON THE
C       Z-AXIS, SET
C
C             IVAR(1,1) = 1      IVAR(1,2) = 2
C             IVAR(2,1) = 3      IVAR(2,2) = 4
C             IVAR(3,1) = 5
C
C       AN OUTPUT BOX COULD LOOK LIKE THIS:
C
C                 -------------------------------
C                /                   /         /!
C               /                   /         / !
C              /                   /         /  !
C             /                   /         /   !
C            /                   /         /    !
C           /                   /         /     !
C          /                   /         /     /!
C         /-------------------/---------/     / !
C         !                   !         !    /  !
C         !                   !         !   /   !
C        E!                   !         !  /    !
C         !                   !         ! /    /
C         !                   !         !/    /
C         !-------------------!---------!    /F
C         !                   !         !   /
C         !                   !         !  /
C        D!                   !         ! /
C         !                   !         !/
C         !-------------------!---------!A
C                   C              B
C
C       WHERE    A  IS THE ORIGIN OF THE COORDINATE SYSTEM
C                B  IS THE FIRST VARIABLE
C                C  IS THE SECOND VARIABLE
C                D  IS THE THIRD VARIABLE
C                E  IS THE FOURTH VARIABLE
C                F  IS THE FIFTH VARIABLE
C
C   INPUT PARAMETERS
C   ----------------
C
C   MM    INTEGER SCALAR (UNCHANGED ON OUTPUT).
C         THE LEADING DIMENSION OF THE MATRIX A.  MUST BE AT LEAST M.
C
C   M     INTEGER SCALAR (UNCHANGED ON OUTPUT).
C         THE NUMBER OF CASES.
C
C   N     INTEGER SCALAR (UNCHANGED ON OUTPUT).
C         THE NUMBER OF VARIABLES.
C
C   A     REAL MATRIX WHOSE FIRST DIMENSION MUST BE MM AND SECOND
C            DIMENSION MUST BE AT LEAST N (UNCHANGED ON OUTPUT).
C         THE DATA MATRIX.
C
C         A(I,J) IS THE VALUE FOR THE J-TH VARIABLE FOR THE I-TH CASE.
C
C   CLAB  VECTOR OF 4-CHARACTER VARIABLES DIMENSIONED AT LEAST N
C            (UNCHANGED ON OUTPUT).
C         THE LABELS OF THE VARIABLES.
C
C   RLAB  VECTOR OF 4-CHARACTER VARIABLES DIMENSIONED AT LEAST M
C            (UNCHANGED ON OUTPUT).
C         THE LABELS OF THE CASES.
C
C   TITLE 10-CHARACTER VARIABLE (UNCHANGED ON OUTPUT).
C         THE TITLE OF THE DATA SET.
C
C   XMIN  INTEGER VECTOR DIMENSIONED AT LEAST N (UNCHANGED ON OUTPUT).
C         XMIN(I) HOLDS THE MINIMUM VALUE TO BE PLOTTED FOR VARIABLE I.
C
C   XMAX  INTEGER VECTOR DIMENSIONED AT LEAST N (UNCHANGED ON OUTPUT).
C         XMAX(I) HOLDS THE MAXIMUM VALUE TO BE PLOTTED FOR VARIABLE I.
C
C         IF XMIN(I) .GE. XMAX(I) ON INPUT, THEIR VALUES WILL BE
C            DETERMINED BY THE ROUTINE.
C
C   NC    INTEGER VECTOR DIMENSIONED AT LEAST N (UNCHANGED ON OUTPUT).
C         NC(I) HOLDS THE MAXIMUM NUMBER OF DIVISIONS FOR VARIABLE I.
C
C         THE TOTAL NUMBER OF SIDE DIVISIONS FOR THE Y AND Z AXES
C            TOGETHER MUST BE NO GREATER THAN 20.  AN ERROR WILL
C            OCCUR OTHERWISE.
C
C   IVAR  INTEGER MATRIX WHOSE FIRST DIMENSION MUST BE 3 AND WHOSE
C            SECOND DIMENSION MUST BE AT LEAST N (UNCHANGED ON OUTPUT).
C         THE FIRST ROW OF IVAR HOLDS THE VARIABLES TO BE PLOTTED ON THE
C            X-AXIS.  THE SECOND AND THIRD ROWS HOLDS THE VARIABLES FOR
C            THE Y-AXIS AND THE Z-AXIS, RESPECTIVELY.
C
C   OUNIT INTEGER SCALAR (UNCHANGED ON OUTPUT).
C         UNIT NUMBER FOR OUTPUT.
C
C   OUTPUT PARAMETER
C   ----------------
C
C   IERR  INTEGER SCALAR.
C         ERROR FLAG.
C
C         IERR = 0, NO ERROR WAS DETECTED DURING EXECUTION
C
C         IERR = 1, THE NUMBER OF SIDE DIVISIONS FOR THE Y- AND
C                   Z-COORDINATES IS GREATER THAN 20.  REDUCE THE
C                   APPROPRIATE VALUES OF NC.
C
C   REFERENCES
C   ----------
C
C     HARTIGAN, J. A. (1975).  CLUSTERING ALGORITHMS, JOHN WILEY &
C        SONS, INC., NEW YORK.  PAGES 39, 56-57.
C
C     HARTIGAN, J. A. (1975) PRINTER GRAPHICS FOR CLUSTERING. JOURNAL OF
C        STATISTICAL COMPUTATION AND SIMULATION. VOLUME 4,PAGES 187-213.
C
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