Newton Interpolation Example - Python

NewtonInterpol.py

print "Diferencias Divididas (Newton)"
n = int(raw_input("Ingrese el grado del polinomio a evaluar: "))+1
matrix = [0.0] * n
for i in range(n):
    matrix[i] = [0.0] * n

vector = [0.0] * n

for i in range(n):
    x = raw_input("Ingrese el valor de x: ")
    y = raw_input("Ingrese el valor de f("+x+"): ")
    vector[i]=float(x)
    matrix[i][0]=float(y)

print vector    
print matrix

point_offset = float(raw_input("Ingrese el punto a evaluar: "))


for i in range(1,n):
    for j in range(i,n):
        print "i=",i,"    j=",j
        print "(",matrix[j][i-1],"-",matrix[j-1][i-1],")/(",vector[j],"-",vector[j-i],")"
        matrix[j][i] = ( (matrix[j][i-1]-matrix[j-1][i-1]) / (vector[j]-vector[j-i]))
        print "matrix[",j,"][",i,"] = ",(matrix[j][i-1]-matrix[j-1][i-1])/(vector[j]-vector[j-i])

for i in range(n):
    print matrix[i]
aprx = 0
mul = 1.0
for i in range(n):
    print "matrix[",i,"][",i,"]","=",matrix[i][i]
    mul = matrix[i][i];
    for j in range(1,i+1):
        mul = mul * (point_offset - vector[j-1])
    aprx = aprx + mul
    
print "El valor aproximado de f(",point_offset,") es: ", aprx