R: 2-way repeated measures ANOVA & pairwise.t.test -

using example proposed field in discovering statistics using r (pag 561) 1-way repeated measures anova:

participant <- gl(8, 4, labels = c("p1", "p2", "p3", "p4", "p5", "p6", "p7","p8" )) animal      <- gl(4, 1, 32, labels = c("stick_insect", "kangaroo_testicle", "fish_eye", "witchetty_grub")) retch       <- c(8, 7, 1, 6, 9, 5, 2, 5, 6, 2, 3, 8, 5, 3, 1, 9, 8, 4, 5, 8, 7, 5, 6, 7, 10, 2, 7, 2, 12, 6, 8, 1)  longbush<-data.frame(participant, animal, retch)  pairwise.t.test(longbush$retch, longbush$animal, paired=true, alternative="two.sided", p.adjust.method="none") 

the result is:

              stick_insect kangaroo_testicle fish_eye kangaroo_testicle 0.00202      -                 -        fish_eye          0.00094      0.92007           -        witchetty_grub    0.22673      0.29867           0.40204  

change bit 'pairwise.t.test', dof (the number of subjects 8):

              stick_insect kangaroo_testicle fish_eye kangaroo_testicle 7            -                 -        fish_eye          7            7                 -        witchetty_grub    7            7                 7 

so far =)

let's simulate 2-way repeated measures anova:

participant <- gl(8, 8, labels = c("p1", "p2", "p3", "p4", "p5", "p6", "p7","p8" )) animal      <- gl(4, 1*2, 64, labels = c("stick_insect", "kangaroo_testicle", "fish_eye", "witchetty_grub")) alive       <- gl(2, 1, 64, labels = c("y", "n")) retch       <- sample(c(1:12), 64, replace = true)  longbush2 <- data.frame(participant, animal, alive, retch)  pairwise.t.test(longbush2$retch, longbush2$animal, paired=true, alternative="two.sided", p.adjust.method="none");  

the pairwise.t.test results are:

              stick_insect kangaroo_testicle fish_eye kangaroo_testicle 0.022        -                 -        fish_eye          0.202        0.584             -        witchetty_grub    0.374        0.041             0.433    

and dof:

              stick_insect kangaroo_testicle fish_eye kangaroo_testicle 15           -                 -        fish_eye          15           15                -        witchetty_grub    15           15                15   

instead, factor alive has 31 dof. interesting.

so, questions: why dof wrongly changed? do wrong?

thank in advance

cheers