一元最小二乘法（c语言实现)

Posted 2021-12-31 _WILLPOWER_

文章目录

• 一元最小二乘法
• python画图验证
• 数据集

一元最小二乘法

🍺

#include <stdio.h>
typedef unsigned int uint;
char filename[] = ".\\\\data.csv";
char str[30];
uint x[50];
uint y[50];
void LeastSquare(uint *x, uint *y, uint lenth, double *a, double *b)

    double sum_x2 = 0, sum_y = 0, sum_x = 0, sum_xy = 0;
    for(int i=0; i< lenth; ++i)
    
        sum_x2 += x[i]*x[i];
        sum_x += x[i];
        sum_xy += x[i]*y[i];
        sum_y += y[i];
    
    *a = (sum_xy*lenth - sum_x*sum_y) / (sum_x2*lenth - sum_x*sum_x);
    *b = (sum_x2*sum_y - sum_x*sum_xy) /(sum_x2 * lenth - sum_x*sum_x);

int main()

    FILE *fp = fopen(filename,"r");
    uint i = 0;
    double a, b;
    fgets(str,30,fp);
    fputs(str,stdout);
    while(1)
    
        if(fscanf(fp,"%u,%u",&x[i],&y[i]) != EOF)
        
            printf("%u,%u\\r\\n",x[i],y[i]);
            i++;
        
        else
            break;
    
    fclose(fp);
    LeastSquare(x, y, 50, &a, &b);
    printf("a is %.2f, b is %.2f", a, b);
    return 0;

python画图验证

🐍

#%%
import pandas as pd
import numpy as np
import matplotlib.pylab as plt
#%%
data = pd.read_csv("./data.csv")
#%%
data.set_index('BOD5',inplace=True)
data = data.sort_index()
#%%
a = 1.924705
b = 76.195741
x1 = np.array(data.index)
y1 = a*x1+b
#%%
data['fitline'] = y1
data.plot()
# data.sort_index().plot()

# %%
plt.plot(x1,y1)
plt.show()
# %%

效果图

数据集

📖

BOD5,CODCr	
375	,809	
341	,734	
258	,559	
614	,1199	
597	,1184	
469	,989	
458	,981	
398	,855	
357	,768	
323	,699	
478	,984	
412	,882	
387	,829	
365	,785	
256	,554	
298	,642	
287	,620	
285	,616	
244	,529	
289	,613	
369	,793	
358	,770	
348	,749	
411	,881	
402,864
399	,857	
357	,768	
362	,789	
342	,763	
289	,624	
287	,619	
268	,579	
322	,694	
411	,845	
325	,701	
347	,777	
356	,766	
329	,709	
298	,643	
276	,596	
258	,559	
298	,643	
249	,539	
246	,544	
348	,749	
368	,791	
384	,826	
410	,880	
458	,998	
388,834