Subroutine:   MINMAX4

Purpose:      Finds the minimum and maximum value and their
              positions in a data array of reals, counting the BLANK
              values. Especially for finding the minimum and maximum
              in a subset.

File:         minmax.c

Author:       K.G. Begeman

Use:          CALL MINMAX4( DATA  ,    Input       REAL ARRAY
                            NDAT  ,    Input       INTEGER
                            AMIN  ,  In/Output     REAL
                            AMAX  ,  In/Output     REAL
                            IMIN  ,  In/Output     INTEGER
                            IMAX  ,  In/Output     INTEGER
                            NBLANK,  In/Output     INTEGER
                            COUNT )  In/Output     INTEGER

              DATA          Data array to operate on.
              NDAT          Number of data points in DATA.
              AMIN          Minimum value.
              AMAX          maximum value.
              IMIN          Offset of minimum.
              IMAX          Offset of maximum.
              NBLANK        Total number of blanks.
              COUNT         On input, the number of data points
                            checked so far, on output the number
                            of data points checked.

Example:      COUNT = 0
              REPEAT
                 CALL GDSI_READ(SET,C1,C2,A,SIZE,N,I_ERR)
                 CALL MINMAX4(A,N,AMIN,AMAX,IMIN,IMAX,NBLANK,COUNT)
              UNTIL (I_ERR .EQ. 0)
              WRITE(*,*) ' The number of blanks is:',NBLANK
              etc.

Note:         If all values in the data array have the BLANK value,
              the minimum and maximum will also be set to BLANK.

Updates:      Jul 22, 1989: KGB, Document created.