Python散點圖和matplotlib

Question

我有一個散點圖，我想繪製一個趨勢線的python。從各種例子我已經在互聯網發現學習如何繪製趨勢線我的代碼如下：

import matplotlib.pyplot as plt 
import numpy as np 

x=np.array([9.80,13.20,13.46,14.09,13.96,10.77,8.79,8.61,8.83,11.08,10.13,12.40,9.90,10.96,12.75,11.79,11.79,12.38,12.78,13.08,12.83,12.57,12.96,12.90,12.91,13.67,12.83,12.50,12.42,12.83,12.82,12.70,12.60,12.90,13.20]) 
y=np.array([0.0706,0.0969,0.0997,0.1031,0.0848,0.1044,0.0815,0.1030,0.0783,0.0970,0.1193,0.0796,0.0697,0.0738,0.0895,0.0912,0.0887,0.0973,0.0942,0.1052,0.0984,0.0965,0.0903,0.0876,0.1071,0.0872,0.0857,0.0967,0.0926,0.0837,0.0967,0.0935,0.0946,0.0930,0.0758 
]) 

plt.scatter(x, y) 
fit = np.polyfit(x, y, deg=4) 
p = np.poly1d(fit) 
plt.plot(x,p(x),"r--") 
plt.show() 

但結果行，而不是作爲一個曲線僅僅是一個線的組合。任何人都可以解釋我的錯誤嗎？

Answer 1

我認爲這是因爲x值沒有排序。看看這個代碼：

import matplotlib.pyplot as plt 
import numpy as np 

x=np.array([9.80,13.20,13.46,14.09,13.96,10.77,8.79,8.61,8.83,11.08,10.13,12.40,9.90,10.96,12.75,11.79,11.79,12.38,12.78, 
      13.08,12.83,12.57,12.96,12.90,12.91,13.67,12.83,12.50,12.42,12.83,12.82,12.70,12.60,12.90,13.20]) 

y=np.array([0.0706,0.0969,0.0997,0.1031,0.0848,0.1044,0.0815,0.1030,0.0783,0.0970,0.1193,0.0796,0.0697,0.0738, 
      0.0895,0.0912,0.0887,0.0973,0.0942,0.1052,0.0984,0.0965,0.0903,0.0876,0.1071,0.0872,0.0857,0.0967,0.0926,0.0837,0.0967,0.0935,0.0946,0.0930,0.0758 ]) 

# Here I sort x values and their corresponding y values 
args = np.argsort(x) 
x = x[args] 
y = y[args] 

plt.scatter(x, y) 
fit = np.polyfit(x, y, deg=4) 
p = np.poly1d(fit) 
plt.plot(x,p(x),"r--") 
plt.show() 

結果：

Answer 2

這樣做：

plt.scatter(x,y) 
x = sorted(x) 
plt.plot(x,p(x),"r--") 

的竅門是在繪製線之前x值進行排序他們。