MinMaxNormalizationFloat Subroutine

private subroutine MinMaxNormalizationFloat(gridIn, gridOut, min, max)

performs a linear transformation on the original data values. Suppose that minX and maxX are the minimum and maximum of feature X. We would like to map interval [minX, maxX] into a new interval [new_minX, new_maxX]. Consequently, every value v from the original interval will be mapped into value new_v following formula:

new_v = (v - minX) / (maxX - minX) * (new_maxX - new_minX) + new_minX

If new_minX and new_maxX are not given values are mapped to [0,1] interval

References:
Hann, J., Kamber, M. (2000). Data Mining: Concepts and Techniques. Morgan Kaufman Publishers.

Arguments

Type IntentOptional Attributes Name
type(grid_real), intent(in) :: gridIn
type(grid_real), intent(inout) :: gridOut
real(kind=float), intent(in), optional :: min
real(kind=float), intent(in), optional :: max

Variables

Type Visibility Attributes Name Initial
integer(kind=short), public :: i
integer(kind=short), public :: j
real(kind=float), public :: new_max
real(kind=float), public :: new_min
real(kind=float), public :: old_max
real(kind=float), public :: old_min

Source Code

SUBROUTINE MinMaxNormalizationFloat &
!
(gridIn, gridOut, min, max) 

IMPLICIT NONE

!Arguments with intent(in):
TYPE (grid_real), INTENT(IN) :: gridIn
REAL (KIND = float), OPTIONAL, INTENT(IN) :: min
REAL (KIND = float), OPTIONAL, INTENT(IN) :: max

!Arguments with intent(inout):
TYPE (grid_real), INTENT(INOUT) :: gridOut

!Local declaration
INTEGER (KIND = short) :: i, j
REAL (KIND = float) :: old_min, old_max
REAL (KIND = float) :: new_min, new_max

!---------------------end of declarations--------------------------------------

!set new_min and new_max
IF (PRESENT(min)) THEN
  new_min = min
ELSE
  new_min = 0.
END IF

IF (PRESENT(max)) THEN
  new_max = max
ELSE
  new_max = 0.
END IF

!get min and max of gridIn
old_min = GetMin (gridIn)
old_max = GetMax (gridIn)

!normalize grid. gridout is supposed to be initialized outside the subroutine
DO i = 1, gridIn % idim
  DO j = 1, gridOut % jdim
    IF (gridIn % mat (i,j) /= gridIn % nodata) THEN
       gridOut % mat (i,j) = (gridIn % mat (i,j) -  old_min) /  &
                             (old_max - old_min) * (new_max - new_min) + new_min
    END IF
  END DO

END DO

RETURN
END SUBROUTINE MinMaxNormalizationFloat