/****************************************************/
/*                                                  */
/*   CSCI 121: Principles of Computer Programming   */
/*   Programming Project #8                         */
/*   Due Monday, March 21st                         */
/*   Programmed by Ian Giese                        */
/*                                                  */
/****************************************************/
#include <iostream>
#include <fstream>
#include <iomanip>
#include <cmath>

using namespace std;

double calcSlope(int n, double sumXY, double sumX, double sumY, double sumX2)
{
       double slope;
       slope = (((n * sumXY) - (sumX * sumY))/((n * sumX2) - pow(sumX, 2)));
       return slope;
}

double calcIntercept(double yBar, double slope, double xBar)
{
       double yInt;
       yInt = yBar - (slope * xBar);
       return yInt;
}

void doReportLine(ofstream &output, double price, double maintCost, double slope,
                  double yInt)
{
     double predCost, error;
     predCost = (slope * price) + yInt;
     error = maintCost - predCost;
     output << fixed << showpoint << setprecision(2) << right;
     output << setw(8) << price << setw(14) << maintCost << setw(14)
            << predCost << setw(11) << error << endl;
}

void doHeadings(ofstream &output, double yInt, double slope)
{
     output << "Lake Side Software - Equipment Maintenance Estimation"
            << endl << endl << right << showpoint << setprecision(4)
            << "Linear Regression Coefficients: m = " << setw(9) << slope
            << setw(36) << "b = " << setw(9) << yInt << endl << endl
            << "Summary of Original Data" << endl << endl << left
            << "Purchase     Maintenance    Predicted" << endl
            << "   Price         Cost          Cost        Error" << endl
            << "--------     -----------    ---------    -------" << endl;
}

int main()
{
    double preCost[101], preMaint[101];
    double sumX, sumX2, sumY, sumXY, xBar, yBar, slope, yInt;
    int counter;
    ifstream input("assign8.txt");
    ofstream output("output8.txt");
    
    counter = 0;
    do
    {
            input >> preCost[counter] >> preMaint[counter] >> ws;
            counter++;
    }
    while(!input.eof());
    
    int j = 0;
    do
    {
            sumX += preCost[j];
            sumX2 += (preCost[j] * preCost[j]);
            sumY += preMaint[j];
            sumXY += (preCost[j] * preMaint[j]);
            j++;
    }
    while(j < counter);
    
    xBar = sumX / counter;
    yBar = sumY / counter;
    
    slope = calcSlope(counter, sumXY, sumX, sumY, sumX2);
    yInt = calcIntercept(yBar, slope, xBar);
    doHeadings(output, yInt, slope);
    for(int j = 0; j < counter; j++)
            doReportLine(output, preCost[j], preMaint[j], slope, yInt);
    
    return 0;
}