Backward integration in time using scipy odeint

Question

Is it possible to integrate any Ordinary Differential Equation backward in time using scipy.integrate.odeint ? If it is possible, could someone tell me what should be the ar

Answer 1

It is not necessary to make a change of variables. Here an example:

import math
import numpy
import scipy
import pylab as p

from math import *
from numpy import *
from scipy.integrate import odeint
from scipy.interpolate import splrep
from scipy.interpolate import splev

g1=0.01
g2=0.01
w1=1
w2=1 
b1=1.0/20.0
b2=1.0/20.0
b=1.0/20.0
c0=0
c1=0.2
wf=1

def wtime(t):
  f=1+c0+c1*cos(2*wf*t)
  return f

def dv(y,t):
  return array([y[1], -(wtime(t)+g1*w1+g2*w2)*y[0]+w1*y[2]+w2*y[3], w1*y[2]-g1*w1*y[0], w2*y[3]-g2*w2*y[0]])

tv=linspace(100,0,1000)
v1zero=array([1,0,0,0])
v2zero=array([0,1,0,0])
v1s=odeint(dv,v1zero,tv)
v2s=odeint(dv,v2zero,tv)

p.plot(tv,v1s[:,0])
p.show()

I check the result with Wolfram Mathematica (that program can solve backward odes).