Python ODEINT problems with args

Question

I am relatively new to Python and trying to use it to solve an integrator problem

x' = - L * x

Where L is the Laplacian Matrix, that is a matrix representation of a graph. This is part of my code:

def integrate_cons(x, t, l):
   xdot = -l*x
   return xdot;

t = np.linspace(0, 10, 101)

#laplacian is a 3x3 matrix
#initial_condition is a vector
solution = odeint(integrate_cons, initial_conditions, t, args=(laplacian,))
print solution

I'm having problems to pass a matrix like an argument in odeint. How can i solve?

Answer 1

import numpy as np
from scipy.integrate import odeint

def integrate_cons(x, t, l):
   # unless you use np.matrix which I never do, you have to use np.dot
   xdot = -np.dot(l,x)
   return xdot;

t = np.linspace(0, 10, 101)
# just a random matrix
l = np.random.rand(3,3)
# initial conditions
x0 = np.array([1,1,1])
#laplacian is a 3x3 matrix
#initial_condition is a vector
solution = odeint(integrate_cons, x0, t, args=(l,))
print(solution)

Look at the scipy cookbook for examples.