myscratchpad

ここがわかりやすかったので、覚書。というかコピペ。官舎

dv <- c(8,6,7,7,6,4,5,5,6,3,5,3,3,6,2,3,4,2,2,3,6,7,5,4,6)
grp <- gl(5,5)

aovres <- aov(dv~grp)
summary(aovres)
model.tables(aovres)

# デフォルトの対比
options()$contrasts
contrasts(grp)

# ヘルマート対比で検定
coef.hel <- contr.helmert(5)
coef.hel
contrasts(grp)  <- coef.hel
aovres.h <- aov(dv~grp)
summary(aovres.h, split=list(grp=c(1,2,3,4)))
#  grp: C1    1 12.100  12.100  9.0299 0.0069971 ** grp1 vs. grp2
#  grp: C2    1 12.033  12.033  8.9801 0.0071289 ** grp1&2 vs. grp3
#  grp: C3    1 19.267  19.267 14.3781 0.0011441 ** grp1&2&3 vs. grp4
#  grp: C4    1  4.840   4.840  3.6119 0.0718780 .  grp1&2&3&4 vs. grp5

# 多項式対比で検定
coef.ply <- contr.poly(5)
coef.ply
contrasts(grp) <- coef.ply
aovres.p <- aov(dv~grp)
summary(aovres.p, split=list(grp=c(1,2,3,4)))

# 自分で対比を設定する
coef.s <- cbind(c(1,-1,1,0,-1), c(-1,-1,-1,4,-1))
coef.s
sum(coef.s)
contrasts(grp) <- coef.s
aovres.s <- aov(dv~grp)
summary(aovres.s, intercept=T, split=list(grp=c(1,2)))
#  grp: C1    1   0.20    0.20   0.1493 0.7033289     # grp1&3 vs. grp2&5
#  grp: C2    1  23.04   23.04  17.1940 0.0004994 *** # grp4 vs. grp1&2&3&5