OLS Matrix procedure
L. Benada
3-factors model:
Yi = a + ßu + ß2i + ßzi + ei
(Yi - Yi) Min.
Partial Derivations
/ n		E™		E™	-AX2i	E™	=1 \			E"=i ^
E™		E™		E™		E™				E™=i ^i^ii
E™	-_1X1i	E™	=1 X2iX\i	E™		E™	:1 X2iX3i		ft	E™=i YiXii
	-_1X1i	E™	:1 X3iXii	Ell	=1 X3iX2i	E™	=1^2 y			E™=i ^j^3i