函数内部'for'迭代的问题

Question

我正在尝试绘制具有不同行为的函数，具体取决于x轴的值。对于超过2.0的x轴（'ec'变量）的值，它是单向的，对于大于此值的值，它以另一种方式起作用。

import numpy as np
import matplotlib.pyplot as plt

ec = np.linspace(0., 3.,20) #range of 'x' axis values

def ten_def(x):
    for i in ec:
        if i <= 2.:
            return 0.85*x*(1-(1-(ec/2))**2) #behavior for ec < than 2.0
        else:
            return 0.85*x  #behavior for ec > 2.0

fcd = float(input('Fck (MPa): '))/1.4

plt.plot(ec, ten_def(fcd), 'b-', ec,(ec*0)+fcd*0.85,'r-')
plt.title('Tensão-deformação')
plt.xlabel('Deformação (‰)')
plt.ylabel('Tensão (MPa)')
plt.show()

代码的绘图部分正在运行。但它绘制了一条曲线，整个曲线具有相同的行为（它始终考虑ec <2.0）。我做错了什么？

Answer 1

您必须返回数据列表作为函数的输出。

import numpy as np
import matplotlib.pyplot as plt

ec = np.linspace(0., 3.,20) #range of 'x' axis values

def ten_def(x):
    result = []
    for i in ec:
        if i <= 2.:
            result.append(0.85*x*(1-(1-(i/2))**2)) #behavior for ec < than 2.0
        else:
            result.append(0.85*x)  #behavior for ec > 2.0
    return result

fcd = float(input('Fck (MPa): '))/1.4

plt.plot(ec, ten_def(fcd), 'b-')
plt.axhline(0.85*fcd, color='r')
plt.title('Tensão-deformação')
plt.xlabel('Deformação (‰)')
plt.ylabel('Tensão (MPa)')
plt.show()

这应该会给你想要的结果