edX problem set 3

ps3_newton.py

def evaluatePoly(poly, x):
    result = 0.0
    for i in range(len(poly)):
        result += poly[i] * x ** i
    return result
# poly = [0.0, 0.0, 5.0, 9.3, 7.0]
# x = -13
# print evaluatePoly(poly, x)

def computeDeriv(poly):
    result = []
    for i in range(1, len(poly)):
        result.append(i * poly[i])
    return result
#poly = [-13.39, 0.0, 17.5, 3.0, 1.0]
#print computeDeriv(poly)

def computeRoot(poly, x_0, epsilon):
    iteration = 0
    fx = evaluatePoly(poly, x_0)
    while abs(fx) >= epsilon:
        fdx = evaluatePoly(computeDeriv(poly), x_0)
        x_0 = x_0 - fx / fdx
        iteration += 1
        fx = evaluatePoly(poly, x_0)
    result = [x_0, iteration]
    return result
    


print computeRoot([-13.39, 0.0, 17.5, 3.0, 1.0], 0.1,  .0001)
print 
print computeRoot([1, 9, 8], -3, 0.01)

print 
print computeRoot([1, -1, 1, -1], 2, 0.001)