class RegLin{
int n; // nombre de points de support
double[] x; // abscisses des points de support
double[] y; // ordonnees des points de support
double a, b; // resultats de la regression : ax+b
RegLin(double[] xdata, double[] ydata) {
x = xdata; y = ydata; n = x.length;
calculCoef();
}
private void calculCoef() {
double sx=0, sx2=0, sy=0, sy2=0, sxy=0;
for (int i=0; i<n; i++) {
sx += x[i]; 
sx2 += x[i]*x[i];
sy += y[i];
sxy += x[i]*y[i];
}

a = (sxy-(sx*sy/n))/(sx2-sx*sx/n);
b = (sy - a*sx) /n;
}
public double geta() {return a;}
public double getb() {return b;}
public double getxi(int i) {return x[i];}
public double getyi(int i) {return y[i];}
public void print() {System.out.println(" a= "+a+" b= "+b);}
//public double calcul(double z) {return a*z+b;}
//public String libelle() {return "regression lineaire";}
}