how to use while(inFile.good()) to keep track of points and sums

[idknuttin]

i have to create a program that finds the best fit line from a file the user enters that contains the points but we dont know how many points there are so i had to use while(inFile.good()). i made the program and it runs however it is not calculating the correct equation. i think i made a mistake where when the file reads the points in the while loop, for example how do i know that each statement is being performed after each x anf y value is being read from the file.

here is my program:

#include<iostream>
#include<cstdlib>
#include<fstream>
#include<cmath>
#include<iomanip>
using namespace std;

int main()
{
    ifstream inFile;
    
    cout << "Enter a file name containing the points: ";
    string inputFilename;
    cin >> inputFilename;
    
    inFile.open(inputFilename.c_str());
    
    double sumx=0;
    double sumy=0;
    double sumxs=0;
    double sumys=0;
    double sumxy=0;
    int n=0;
    
    double x, y;
    int c;
    char p;
    while(inFile.good())
    {
        inFile >> c >> x >> p >> y; //how do i know that after each x and y value is entered
                 //the program completes the following statements to keep
                 //track of sums and how many points there are?
        sumx+=x; //to find the sum of x values
        sumy+=y; //to find the sum of y values
        sumxs+=pow(x,2); //to find the sum of x squared values
        sumys+=pow(y,2); //to find the sum of y sqaured values
        sumxy+=(x*y); //to find the sum of product of x and y values
        n++; //to keep track of how many points there are to find averages
    }
    
    double avgx=sumx/n; //to find the average of x values
    double avgy=sumy/n; //to find the average of y values
    double avgxs=sumxs/n; //to find the average of x squared values
    double avgys=sumys/n; //to find the average of y squared values
    double avgxy=sumxy/n; //to find the average of product x and y values
    
    double a=(avgxy-avgx*avgy)/(avgxs-pow(avgx,2)); //to calculate a
    double b=avgy-(a*avgx); //to calculate b
    
    cout << "The best fit line is given by y="
    << a << "x" << showpos << b <<endl; //y=ax+b
    
    system("PAUSE");
    return 0;

here is what the file with the points looks like:

1 2.2
2 3.4
3 2.9
4 3.5
5 4.9
6 5.2
7 5.5
8 8.4
9 9.2
10 9.4

i think the problem is the periods in the file, cause when i changed them to commas my program would give my the correct answer, so how does the program read periods? is it a char? or something else?

thank you.

[MiiNiPaa]

'.' symbol is decimal separator. 2.2 is read as single floating point number.
And anyway, you should loop on input operations or check stream state right after reading:

while(inFile >> c >> x >> p >> y) {
     //...
}

//or

inFile >> c >> x >> p >> y;
if(!infile)
    break;