To under stand the factor models geomet ric ally, a brief intro duc tion to the repres ent a tion of vari ables and factors as vectors in space is given in Section 4.1, Representing Variables and Factors Geometrically. Section 4.1 is a present a tion of the multivari ate linear model where it is assumed that scores for factors and vari ables are known in addi tion to the factor pattern.