from mpl_toolkits.mplot3d import Axes3D  
from matplotlib import cm  
from matplotlib.ticker import LinearLocator, FormatStrFormatter  
import matplotlib.pyplot as plt  
import math
import numpy as np
from numpy import *;#导入numpy的库函数
import pylab as pl
c=100.
l=50.
w=2*math.pi*c/l
deltax=1
deltat=deltax/c
r=0.9979

t=[0]
y=np.zeros( (1,100) )
y_old=np.zeros( (1,100) )
Y=[y,y]
while t[-1]<100.25:
    for i in range(100):
        y_old=Y[-2]# 保留前两次运算的结果
        #迭代过程：
        if i==0 :
            y[0][i]=math.sin(w*t[-1])
        elif i==99:
            y[0][i]=0
        else:
            y[0][i]=2*(1-r*r)*y[0][i]-y_old[0][i]+r*r*(y[0][i+1]+y[0][i-1])
        Y.append(y)
    t.append(t[-1]+deltat)
ys=y.flatten()
print('r=',r,'波长=',l,'波速c=',c,'运行时常：',100.25)
x in range (100)
plt.plot(x,ys)