myscratchpad

処理対比 (treatment contrast)
> contr.treatment(3)
  2 3
1 0 0
2 1 0
3 0 1

SASっぽい対比
> contr.SAS(3)
  1 2
1 1 0
2 0 1
3 0 0

零和対比 (zero sum contrast)
> contr.sum(3)
  [,1] [,2]
1    1    0
2    0    1
3   -1   -1

ヘルマート対比 (helmert contrasts)
> contr.helmert(3)
  [,1] [,2]
1   -1   -1
2    1   -1
3    0    2

多項式対比 (polynomial contrast)
> contr.poly(3)
            .L     .Q
[1,] -7.07e-01  0.408
[2,] -9.07e-17 -0.816
[3,]  7.07e-01  0.408


# 現在の対比係数を調べる
> options()$contrasts
        unordered           ordered
"contr.treatment"      "contr.poly"

# 対比係数を変える
options(contrasts = c("contr.sum", "contr.sum"))