trying to solve 2 first order differential equations, python

问题

I am trying to solve these 2 equations bellow and I am having no luck, if anyone can point out where i am going wrong that would be great thanks!

def f(t,alpha):
    return t*t/(2*alpha) * (1-sqrt(1-4*alpha))

def f_1 (t,x,params):
    alpha=params[0]
    return [X[1],-((3/f(t,alpha)*X[0]))]

T=ode_solver()
T.y_0=[1,0]
T.function=f_1
T.scale_abs=[1e-4,1e-4,1e,-5]
T.error_rel=1e-4
T.ode_solve(t_span[0,1000],params=[0.001],num_points=1000)
T.plot_solution(i=0)

回答1:

Try using scipy. Look this example:

from scipy.integrate import odeint
from pylab import * # for plotting commands

def deriv(y,t, alpha): # return derivatives of the array y #edit: put an extra arg
    #use the arg whatever you want
    a = -2.0
    b = -0.1
    return array([ y[1], a*y[0]+b*y[1] ])

time = linspace(0.0,10.0,1000)
yinit = array([0.0005,0.2]) # initial values
alpha = 123 #declare the extra(s) agrg
y = odeint(deriv,yinit,time,args=(alpha, )) #pass the extras args as tuple
figure()

plot(time,y[:,0]) # y[:,0] is the first column of y
xlabel('t')
ylabel('y')
show()

Result:

Font: http://bulldog2.redlands.edu/facultyfolder/deweerd/tutorials/Tutorial-ODEs.pdf

An interesting link: http://docs.scipy.org/doc/scipy-0.14.0/reference/generated/scipy.integrate.ode.html

来源：https://stackoverflow.com/questions/27270547/trying-to-solve-2-first-order-differential-equations-python