RuntimeWarning:在除法中遇到无效的值 [英] RuntimeWarning: invalid value encountered in divide

问题描述

我必须使用欧拉方法为弹簧中的球"模型编写程序

I have to make a program using Euler's method for the "ball in a spring" model

from pylab import*
from math import*
m=0.1
Lo=1
tt=30
k=200
t=20
g=9.81
dt=0.01
n=int((ceil(t/dt)))
km=k/m
r0=[-5,5*sqrt(3)]
v0=[-5,5*sqrt(3)]
a=zeros((n,2))
r=zeros((n,2))
v=zeros((n,2))
t=zeros((n,2))
r[1,:]=r0
v[1,:]=v0
for i in range(n-1):
    rr=dot(r[i,:],r[i,:])**0.5
    a=-g+km*cos(tt)*(rr-L0)*r[i,:]/rr
    v[i+1,:]=v[i,:]+a*dt
    r[i+1,:]=r[i,:]+v[i+1,:]*dt
    t[i+1]=t[i]+dt

    #print norm(r[i,:])

plot(r[:,0],r[:,1])
xlim(-100,100)
ylim(-100,100)
xlabel('x [m]')
ylabel('y [m]')

show()

我不断收到此错误:

a=-g+km*cos(tt)*(rr-L0)*r[i,:]/rr
RuntimeWarning: invalid value encountered in divide

我不明白，代码有什么问题?

I can't figure it out, what is wrong with the code?

推荐答案

我认为您的代码正在尝试除以零"或除以 NaN".如果您知道这一点并且不想让它困扰您，那么您可以尝试:

I think your code is trying to "divide by zero" or "divide by NaN". If you are aware of that and don't want it to bother you, then you can try:

import numpy as np
np.seterr(divide='ignore', invalid='ignore')

有关更多详细信息，请参见:

For more details see:

• http://docs.scipy.org/doc/numpy/reference/generated/numpy.seterr.html

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