euler

# Hello World program in Python
# Euler method in Python - 
from __future__ import division
from math import exp
import matplotlib.pyplot as plt
import numpy as np

h=0.01
x0=0
y0=1
xmax=4
x=x0
y=y0

print "Euler method\n"
puntsEuler=[]
while x<=xmax:
    puntsEuler.append((x,y))
    print x,y
    k1=(-2*x**3+12*x**2-20*x+8.5)
    y = y + h*k1
    x = x + h
#puntsEuler.append((x,y))
print x,y
print puntsEuler


print '===   Euler   ===='
for i in range(len(puntsEuler)):
    print puntsEuler[i][0],' --> ',puntsEuler[i][1]
print
print '============='


# dibuixant els punts i la solucio 

def f(z):
    return -0.5*z**4+4*z**3-10*z**2+8.5*z+1

te, eu = zip(*puntsEuler)
#tr, rk = zip(*puntsRK)

t1 = np.arange(x0, xmax, h/10)

plt.plot(te,eu,'b-',marker='o')
#plt.plot(tr,rk,'g-',marker='*')
plt.plot(t1,f(t1),'r')
plt.show()