GetSumOfGridInteger Function

FUNCTION GetSumOfGridInteger &
!
(grid, maskReal, maskInteger) &
!
RESULT (sum)

IMPLICIT NONE

!Arguments with intent(in):
TYPE (grid_integer), INTENT(IN) :: grid
TYPE (grid_real), OPTIONAL,  INTENT(IN) :: maskReal
TYPE (grid_integer), OPTIONAL,  INTENT(IN) :: maskInteger


!Local declarations:
INTEGER (KIND = long) :: sum
INTEGER (KIND = long) :: i, j
!---------------------------end of declarations--------------------------------
sum = 0.
!check that grid and mask have the same coordinate reference system
IF (PRESENT (maskReal)) THEN
    IF ( .NOT. CRSisEqual(maskReal,grid) ) THEN
        CALL Catch ('error', 'GridStatistics',  &
        'calculate mean: ', argument = &
        'coordinate reference system of mask differs from input grid' )
    END IF

    DO j = 1, maskReal % jdim
        DO i = 1, maskReal % idim
            IF (maskReal % mat(i,j) /= maskReal % nodata) THEN
                sum = sum + grid % mat (i,j)
            END IF
        END DO
    END DO
ELSE IF (PRESENT (maskInteger)) THEN
    IF ( .NOT. CRSisEqual(maskInteger,grid) ) THEN
        CALL Catch ('error', 'GridStatistics',  &
        'calculate mean: ', argument = &
        'coordinate reference system of mask differs from input grid' )
    END IF

    DO j = 1, maskInteger % jdim
        DO i = 1, maskInteger % idim
            IF (maskInteger % mat(i,j) /= maskInteger % nodata) THEN
                sum = sum + grid % mat (i,j)
            END IF
        END DO
    END DO

ELSE
    DO j = 1, grid % jdim
        DO i = 1, grid % idim
            IF (grid % mat(i,j) /= grid % nodata) THEN
                sum = sum + grid % mat (i,j)
            END IF
        END DO
    END DO
END IF

RETURN

END FUNCTION GetSumOfGridInteger