Subroutine:   MINMAX3

Purpose:      Finds the minimum and maximum value 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 MINMAX3( DATA  ,    Input       REAL ARRAY
                            NDAT  ,    Input       INTEGER
                            AMIN  ,  In/Output     REAL
                            AMAX  ,  In/Output     REAL
                            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.
              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 MINMAX3(A,N,AMIN,AMAX,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.