功能裏的'for'迭代的問題

Question

我試圖繪製一個具有不同行爲的函數，具體取決於x軸的值。對於x軸（'ec'變量）小於2.0的值，它的行爲是單向的，對於大於這個值的值，它以另一種方式起作用。

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() 

代碼的繪圖部分正在工作。但是它繪製了一條曲線，它對於整個地塊具有相同的行爲（它始終在考慮EC < 2.0）。我究竟做錯了什麼？

Answer 1

您必須返回數據的列表作爲函數的輸出。

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() 

這應該給你想要的結果