Implementation of the least squares C language __c language

1. Experimental purposes:

Further familiar with the least square method of curve fitting.

Master programming language character processing program design and debugging techniques.

2. Experimental requirements:

Input: The number of known points and the coordinates of each point.

Output: The fitting curve is obtained according to the principle of least squares and the coordinates of each point.

3. Program Flow:

(1) Enter the number of known points;

(2) input the x coordinates of the known points respectively;

(3) Enter the y-coordinate of the known point respectively;

(4) The fitting curve is obtained by calling the function.

The principle of least squares is as follows:

According to a set of experimental data, the letter of the variable x and the dependent variable y is obtained.

4. It is difficult to find out the coefficients of polynomials according to the known coordinate points. 5. Program Flow Chart

6. Source code (This procedure has passed the test)

#include <stdio.h> #include <math.h> #define X #define Y float x[x],y[y]; The total number of data entered by int n;//is the total number of coordinates void init ();//initializes and enters the relevant data void Confrim (),//confirms the entered data void Deal (), or calculates the fitting curve void modify () according to the input coordinate point;
	/used to modify the corresponding coordinates of the error to avoid some data re-enter void main () {int select;
	System ("Color F1");//dos command makes the interface variable color init ();//Confrim ();
	printf ("Select the number of polynomials to be synthesized (hint: Enter 2 if the function is typed 12 times):");
scanf ("%d", &select)//Enter the number of times you want to select the Fitted function deal (select);
	void init ()//Initialize and enter related data {int i;
	printf ("\n*********************************************************\n");
	printf ("\ n Welcome to use least squares data handler \ n");
	
	printf (\ nplease Enter the number of groups of data you want to process (hint: The program defines a pair of x,y values as a set of data): ");
		while (1) {scanf ("%d", &n);
			if (n<=1) {printf ("\ n Group number of data cannot be less than or equal to 1");
		printf ("Please re-enter the number of groups of data you want to process:");
			else if (n>50) {printf ("\ n Sorry, this procedure is temporarily unable to handle more than 50 groups of data");
		printf ("Please re-enter the number of groups of data you want to process:");
	else break;
		for (i=0;i<n;i++)//Enter the corresponding coordinates to be stored in the array {printf ("\ n Enter the value of%d x x%d=", i+1,i+1);
		scanf ("%f", &x[i]); printf ("\ n Please enter a value for the corresponding Y": y%d= ", i+1);
	scanf ("%f", &y[i]);
	System ("color F2");//System ("CLS");/clear Screen} void deal (int select)//Use the Kramer rule to solve the equation {int i;
	float A0,A1,A2,TEMP,TEMP0,TEMP1,TEMP2; Float sy=0,sx=0,sxx=0,syy=0,sxy=0,sxxy=0,sxxx=0,sxxxx=0;//defines the correlation variable for (i=0;i<n;i++) {sx+=x[i];//computed XI and sy+=y[i];/ /Compute the sum of the squares of the sxx+=x[i]*x[i];//and the Sxxx+=pow (x[i],3);//compute the cubic and sxxxx+=pow (x[i],4) of Xi and the sum of the 4 squares of Xi
	The determinant of the coefficients of the temp=n*sxx-sx*sx;//equation of Xi squared by Yi and the sxxy+=x[i]*x[i]*y[i];//calculated by Xi by Yi are temp0=sy*sxx-sx*sxy;
	TEMP1=N*SXY-SY*SX;
	A0=temp0/temp;
	A1=temp1/temp; 
		if (select==1) {printf ("one-dimensional linear equation obtained by least squares fitting is: \ n"); 
				printf ("F (x) =%3.3fx+%3.3f\n", a1,a0);
	System ("pause");
	The coefficients determinant +sxx* (sx*sxxx-sxx*sxx) of the temp=n* (sxx*sxxxx-sxxx*sxxx)-sx* (sx*sxxxx-sxx*sxxx)//equation;
	temp0=sy* (sxx*sxxxx-sxxx*sxxx)-sxy* (sx*sxxxx-sxx*sxxx) +sxxy* (SX*SXXX-SXX*SXX);
	temp1=n* (sxy*sxxxx-sxxy*sxxx)-sx* (SY*SXXXX-SXX*SXXY) +sxx* (SY*SXXX-SXY*SXX); temp2=n* (sxx*sxxy-sxy*sxxx)-sx* (sx*sxxy-sy*sxxx) +sxx* (sX*SXY-SY*SXX);
	A0=temp0/temp;
	A1=temp1/temp;
	A2=temp2/temp; 
		if (select==2) {printf ("two approximate equations obtained by least squares fitting: \ n"); 
		printf ("F (x) =%3.3fx2+%3.3fx+%3.3f\n", a2,a1,a0);
	System ("pause");
	} void Modify ()//modify the corresponding coordinate of the error ({int z);
	char flag;
		while (1) {printf ("Please enter the first set of data you want to modify:");
		scanf ("%d", &z);
		printf ("\ n Please enter the value of the%d x you want to modify x%d=", z,z);
		scanf ("%f", &x[z-1]);
		printf ("\ n Please enter the value of the corresponding y you want to modify: y%d=", z);
		scanf ("%f", &y[z-1]);
		printf ("Whether to continue modifying the data is y no n:");
		GetChar ();
		scanf ("%c", &flag); if (flag== ' N ' | |
	flag== ' n ') break;
System ("CLS");//Clear screen Confrim ();
	} void Confrim () {char flag;
	int i;
			while (1) {for (i=0;i<n;i++) {printf ("Please enter the value of%d x x%d=", i+1,i+1);
			printf ("%f", X[i]);
			
			printf ("Enter the value of the corresponding y: y%d=", i+1);
			printf ("%f", Y[i]);
		printf ("\ n");
		printf ("Confirm that the data you entered is y no n (ie re-enter) modify M:");
		GetChar ();
		scanf ("%c", &flag); if (flag== ' y ') | |
		flag== ' Y ') break; else if (flag== ' n ' | |
		flag== ' N ') init ();
			else {modify ();
		Break
}
	}	
} 

Test

1 Fitting two curve results (in the book)

2. Fitting a curve result