Собственно, вот:

#!/usr/bin/awk

BEGIN	{
	N = 0; X = 0; Y = 0; XY = 0; XX = 0;
}

/^-?[0-9]/	{
	N += 1;
	X += $1;
	XX += $1*$1;
	Y += $2;
	XY += $1*$2;
}

END {
	b = (N*XY - X*Y)/(N*XX - X*X);
	a = (Y - b*X)/N;

	printf "N = %d, y = %g * x + %g\n", N, b, a
}