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// Regression is a class to compute a linear regression
//
#include "regression.h"
Regression::Regression()
{
init();
}
void Regression::init()
{
sumxx = 0;
sumyy = 0;
sumxy = 0;
sumx = 0;
sumy = 0;
n = 0;
}
void Regression::point(float x, float y)
{
sumx = sumx + x;
sumy = sumy + y;
sumxx = sumxx + x * x;
sumyy = sumyy + y * y;
sumxy = sumxy + x * y;
n = n + 1;
}
void Regression::regress()
{
float sxx = sumxx - sumx * sumx / n;
float sxy = sumxy - sumx * sumy / n;
b = sxy / sxx;
a = (sumy - b * sumx) / n;
}
float Regression::f(float x)
{
return a + b * x;
}
float Regression::f_inv(float y)
{
return (y - a) / b;
}
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