[LA] Orthogonal contrasts

Definition(one contrast): linear combination of group mean vectors Φ=∑Gg=1cgμ^g is a contrast if ∑Gg=1cg=0
Definition(two contrasts): two contrasts Φ1=∑Gg=1cgμ^g and Φ2=∑Gg=1dgμ^g are orthogonal if ∑Gg=1cgdgng=0

application can be found in
http://blog.csdn.net/comeyan/article/details/50514596