while 和 for 循环中的 Python 索引问题

Question

我正在调整 Schorsch 在 While loop inside for loop in Matlab 中的回答，以便在 Python 3.5 中使用来解决我的问题。

我想遍历 t 数组中的值。对于每个值，如果我的计算结果z 收敛（或在最大迭代次数后不收敛）我将其复制到数组中。然后我绘制结果。

import numpy as np
import matplotlib.pyplot as plt

maxiter = 100 # max no. iterations in convergence loop
t = 0.05*np.arange(10)
z = 0.1 # initial guess
x = np.zeros(len(t)) # array for results
cvec = np.zeros(len(t)) # does loop converge?

for ii in t:

    print(ii)

    convergence = 0

    while convergence == 0:

        z_old = z
        z = ii*np.random.rand() # perform calculations

        # check convergence

        if abs(z-z_old) < 0.01: # convergence
            # store result
            convergence = 1
            x[ii] = z
            cvec[ii] = convergence

        elif abs(z-z_old) >= 0.01 and ii < maxiter: # no convergence but loop again
            convergence = 0
        else: # no convergence, move on to next value in t array
            convergence = 0
            x[ii] = 1e3
            cvec[ii] = convergence
            break

# plot result
plt.figure()
plt.plot(t[cvec==1],x[cvec==1],'x')
plt.xlabel('t')
plt.ylabel('x')
plt.show()

我收到一个错误：VisibleDeprecationWarning: using a non-integer number instead of an integer will result in an error in the future lines = """

这是否意味着我必须更改索引while 或for 循环的方式，如果是，我应该怎么做？

Answer 1

问题与x[ii] = 和cvec[ii] 行有关。当您尝试访问非整数索引时。 这些索引是在以下行生成的：

(...)
t = 0.05*np.arange(10) #[ 0.  ,  0.05,  0.1 ,  0.15,  0.2 ,  0.25,  0.3 ,  0.35,  0.4 ,  0.45]
(...)

要解决此问题，有多种方法可以解决，但最简单的方法是访问与 t 变量中的值相同的索引。

import numpy as np
import matplotlib.pyplot as plt

maxiter = 100 # max no. iterations in convergence loop
t = 0.05*np.arange(10)
z = 0.1 # initial guess
x = np.zeros(len(t)) # array for results
cvec = np.zeros(len(t)) # does loop converge?

for idx, ii in enumerate(t):

    print(ii)

    convergence = 0

    while convergence == 0:

        z_old = z
        z = ii*np.random.rand() # perform calculations

        # check convergence

        if abs(z-z_old) < 0.01: # convergence
            # store result
            convergence = 1
            x[idx] = z
            cvec[idx] = convergence

        elif abs(z-z_old) >= 0.01 and ii < maxiter: # no convergence but loop again
            convergence = 0
        else: # no convergence, move on to next value in t array
            convergence = 0
            x[idx] = 1e3
            cvec[idx] = convergence
            break

# plot result
plt.figure()
plt.plot(t[cvec==1],x[cvec==1],'x')
plt.xlabel('t')
plt.ylabel('x')
plt.show()

---

使用while循环迭代一个值的最大次数，而它不收敛

import numpy as np
import matplotlib.pyplot as plt

maxiter = 100 # max no. iterations in convergence loop
t = 0.05*np.arange(10)
z = 0.1 # initial guess
x = np.zeros(len(t)) # array for results
cvec = np.zeros(len(t)) # does loop converge?

for idx, ii in enumerate(t):

    print(ii)

    # Assume it wont converge
    # So if we loop through all the max iterations and still no convergence, it is already marked
    x[idx] = 1e3
    cvec[idx] = 0

    while iter in range(maxiter):

        z_old = z
        z = ii*np.random.rand() # perform calculations

        if abs(z-z_old) < 0.01: # converge, therefore stop looping
            x[idx] = z
            cvec[idx] = 1
            break

# plot result
plt.figure()
plt.plot(t[cvec==1],x[cvec==1],'x')
plt.xlabel('t')
plt.ylabel('x')
plt.show()