# -*- coding: utf-8 -*-
"""
Created on Mon Dec 08 10:54:02 2014

@author: grivet

Listing 2.1 : Polynomes de Legendre, calcul par rˇcurrence sur n

"""
import numpy as np
import matplotlib.pyplot as plt

def legendre(n,x):
    if n == 0:
        return 1.0
    elif n == 1:
        return x
    else:
        pavder = 1; pder = x; i = 1
        while i<n:
            pp = ((2*n+1)*x*pder - n*pavder)/(n+1)
            pavder = pder; pder = pp
            i = i+1
    return pp
n = eval(input('indice: '))
x = np.linspace(-1.0,1.0,200)
plt.plot(x,legendre(n,x))
plt.show()