Numpy Error: Operands could not be broadcast together with shapes (2,) (0,)

Question

我正在尝试创建一个二维数组，其中的值取自数组的先前值，并添加到从函数计算的值中。但是我收到错误：

ValueError: operands could not be broadcast together with shapes (2,) (0,)

现在虽然我知道错误的含义，但我似乎无法找到问题的确切位置或解决方法。

该程序的用途是创建一个自定义欧拉求解器，它使用函数

添加数组的先前值

代码：

import numpy as np
from scipy.integrate import odeint


def func(): 
    d1 = #equation
    d2 = #equation
    return [[d1], [d2]]

l = 1
m = 1
g = 1
mu = 1

max = 1

arr_in = np.array(1, 1)

arr_2 = np.linspace(1, 4, maxx) 
dt = 1

arr_out = np.zeros((max, 2))
arr_out[0] = arr_in[0]
for i in range(len(arr_2)):
    arr_out[i+1] = arr_out[i] + func(arr_out[i-1], arr_2[i-1], l, m, g, mu) * dt

回溯：

Traceback (most recent call last):
  File "task3.py", line 31, in <module>
    res_arr[i] = solver(res_arr, i)
ValueError: could not broadcast input array from shape (2,2) into shape (2,)

Answer 1

您要么缺少一对括号：

for i in range(len(time_arr)):
    #              v                                                                v
    res_arr[i+1] = (res_arr[i] + pend_func(res_arr[i-1], time_arr[i-1], l, m, g, mu)) * dt
    #              ^                                                                ^

或者需要将pend_func的return类型转换为np.array:

for i in range(len(time_arr)):
    #                           vvvvvvvvv                                                   v
    res_arr[i+1] = res_arr[i] + np.array(pend_func(res_arr[i-1], time_arr[i-1], l, m, g, mu)) * dt
    #                           ^^^^^^^^^                                                   ^

两者都能解决问题，但会产生不同的结果，所以我不确定哪一个适合您的目的。

Answer 2

问题是 pend_func 函数返回的数组与其余数组的形状不同。这是通过更改

修复的

return [[d1], [d2]]

至

return [d1, d2]

Numpy Error: Operands could not be broadcast together with shapes (2,) (0,)

Numpy Error: Operands could not be broadcast together with shapes (2,) (0,)

python

arrays

numpy

multidimensional-array