只有长度为 1 的数组可以转换为 Python 标量
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only length-1 arrays can be converted to Python scalars
提问by Bogdan Osyka
Hei I am trying to get a plot for the following problem: U (x) =U0, if |x| ≥ x0 U (x)=U0*|x|/x0 if |x| < x0
嘿，我正在尝试绘制以下问题的图：U (x) = U0, if |x| ≥ x0 U (x)=U0*|x|/x0 如果 |x| < x0
and programm:
和程序：
from pylab import*
x_0=5
U_0=200
#U_x=zeros(n,1)
#x=zeros(n,1)
x=arange(-20,20,0.01)
if float(abs(x))>=x_0:
U_x=U_0
elif float(abs(x))<x_0:
U_x=U_0*(float(abs(x))/x_0)
fig=figure()
suptitle("a)")
fig.subplots_adjust(hspace=0.5)
plot(x,U_x)
xlabel('x [m]')
ylabel('U_x [J]')
show()
But I always get this mistake:
但我总是犯这个错误：
if float(abs(x))>=x_0:
TypeError: only length-1 arrays can be converted to Python scalars
Please help:)
请帮忙：）
采纳答案by HYRY
abs(x) is an array, you can't convert the array to a float value, that is the error. You can write a for loop to do the calculation, but numpy can do vectorized if condition by numpy.where. For more information, read the document:
abs(x) 是一个数组，您不能将数组转换为浮点值，这是错误。您可以编写一个 for 循环来进行计算，但 numpy 可以对 if 条件进行矢量化numpy.where。有关更多信息，请阅读文档：
import numpy as np
x = np.arange(-20, 20, 0.01)
x0 = 5
U0 = 200
u = np.where(np.abs(x) >= x0, U0, U0*np.abs(x)/x0)
plot(x, u, lw=3)
output:
输出：
You can also use piecewisefunction, it can deal with more complicated case.
您也可以使用分段函数，它可以处理更复杂的情况。
