我試圖給一個圖形添加一個三次函數而不是一個線性趨勢線

Question

這個x和y是數據列表，用線性趨勢線繪製得很好。
我還想添加一個三次趨勢線。

import matplotlib.pyplot as plt 
x = (distanceList) 
y = (percentCopper) 
plt.scatter(x,y) 
title = "trendLine" 
xLabel = "Distance m" 
yLabel = "percent copper" 
plt.title (title, fontsize=10); 
plt.ylabel(yLabel, fontsize=10); 
plt.xlabel(xLabel, fontsize=10); 
fit = np.polyfit(x,y,1) 
fit_fn = np.poly1d(fit) 
plt.plot(x, y, '.', x, fit_fn(x), 'r') 
plt.xlim(0, 50) 
plt.ylim(0, 2.5) 
plt.show() 

Answer 1

只要使用np.polyfit(x,y,3)並將其添加到情節，像下面的代碼：

import matplotlib.pyplot as plt 
import numpy as np 
x = np.array(range(50)) 
y = x**3/5000.0-x/5000.0 
plt.scatter(x,y) 
title = "trendLine" 
xLabel = "Distance m" 
yLabel = "percent copper" 
plt.title (title, fontsize=10); 
plt.ylabel(yLabel, fontsize=10); 
plt.xlabel(xLabel, fontsize=10); 
fit = np.polyfit(x,y,1) 
fit3 = np.polyfit(x,y,3) 
fit_fn = np.poly1d(fit) 
fit_fn3 = np.poly1d(fit3) 
plt.plot(x, y, '.', x, fit_fn(x), fit_fn3(x), 'r') 
plt.xlim(0, 50) 
plt.ylim(0, 2.5) 
plt.show()