INTERPOLATION DEMONSTRATION

!———————————————————————--
SUBROUTINE newtonForm(arr, row, str)
	IMPLICIT NONE
	REAL, DIMENSION(4,2) :: arr
	REAL, DIMENSION(4,5) :: mydata
	REAL, DIMENSION(5) :: yint
	REAL :: xterm
	INTEGER :: row, i, j
	CHARACTER(5) :: str
	mydata(1:4, 1:5) = 0
	yint(1:5) = 0
	
	!Store x values
	mydata(1:4,1) = arr(1:4,1)
	!Store y values
	mydata(1:4,2) = arr(1:4,2)
	
	DO j = 3,5,1
		DO i = 1,(6-j),1
			mydata(i, j) = (mydata(i+1, j-1) - mydata(i, j-1)) / (mydata(i+j-2,1) - mydata(i,1))
		ENDDO
	ENDDO
	xterm = 1
	yint(1) = mydata(1,2)
	IF (str == ’upper’) THEN
		DO i = 1,4,1
			xterm = xterm * (upper(row,1) - mydata(i,1))
			upper(row,3) = yint(1) + mydata(1,i+1) * xterm
			yint(i+1) = upper(row,2)
		ENDDO
	ELSEIF (str == ’lower’) THEN
		DO i = 1,4,1
			xterm = xterm * (lower(row,1) - mydata(i,1))
			lower(row,3) = yint(1) + mydata(1,i+1) * xterm
			yint(i+1) = lower(row,2)
		ENDDO
	ENDIF
	
END SUBROUTINE newtonForm
!———————————————————————--
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END PROGRAM newtonPoly