Implementation of C + + by least squares method

Source: http://blog.csdn.net/qll125596718/article/details/8248249

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Ask for A, B value:

Ordinary Least Square.cpp: Defines the entry point of the console application.

//

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#include"stdafx.h"

#include<iostream>

#include<fstream>

#include<vector>

Usingnamespace std;

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Class Leastsquare

{

???? Double A, b;

Public:

???? Leastsquare (const vector<Double>& x, const vector<double>& y) //Least Squares formula

???? {

???????? double t1 = 0, t2 = 0, t3 = 0, T4 = 0;

???????? for (int i = 0; i < x.size (); ++i)

???????? {

???????????? T1 + = x[i] * X[i];

???????????? T2 + = X[i];

???????????? T3 + = x[i] * Y[i];

???????????? T4 + = Y[i];

????????}

???????? A = (T3 * x.size ()-T2 * T4)/(T1 * x.size ()-T2 * T2);

???????? b = (T1 * t4-t2 * T3)/(T1 * x.size ()-T2 * T2);

????}

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???? double GetY (constdouble x) const

???? {

???????? return A * x + b;

????}

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???? void print () const

???? {

???????? cout << "y =" << a << "x +" << b << endl;

????}

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};

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int _tmain (int argc, _tchar* argv[])

{

???? if (argc! = 2)

???? {

???????? cout << "Usage:DataFile.txt" << Endl;

???????? return -1;

????}

???? Else

???? {

???????? vector<Double> x;

???????? Ifstream in (argv[1]);

???????? for (double d, in >> D;)//To put the read value all in container x

???????? {

???????????? X.push_back (d); //push_back () is an element that is placed at the end of the container, which is equivalent to adding an element at the end

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????????}

???????? int sz = x.size ();

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???????? vector<Double> Y (x.begin () + SZ/2, x.end ()); Put all the elements in the remaining container x into the container y

???????? X.resize (SZ/2); //Adjust the length of container x to remove elements that exceed the current size

???????? Leastsquare ls (x, y); //Call the least squares to find a and b

???????? Ls.print ();

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???????? cout << "Input x:\n";

???????? double x0;

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???????? while (Cin >> x0)

???????? {

???????????? cout << "y =" << ls.gety (x0) << Endl;

???????????? cout << "Input x:\n";

????????}

????}

???? return 0;

}

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Experimental simulation data:

10	15	20	25	30	35	40	45
2000.36	2000.50	2000.72	2000.80	2001.07	2001.25	2001.48	2001.60

Experimental results:

Implementation of C + + by least squares method