[R] post-hocs with multiple factors (anovas)?

[Greg Trafton]

Hi, all.  I'm working on post hoc comparisons on anovas with multiple
factors.  the design is 1 repeated measure (session) and 1 between measure
(cond).  my dependent measure is rl.  here is the data I'm using (in a
data.frame):

mig <- data.frame(subj=factor(rep(subj,3)),
                  cond=factor(rep(cond,3)),
                  session=factor(c(rep(1,nsubj),rep(2,nsubj),rep(3,nsubj))),
                  rl)
> mig
    subj cond session      rl
1  401.1   NW       1  6.4081
2  402.1   NW       1  5.8861
3  500.1  NWC       1  5.3492
4  502.1  NWC       1  8.5302
5  601.1  NWR       1  2.7519
6  602.1  NWR       1  4.5404
7  603.1  NWR       1  4.3442
8  604.1  NWR       1  3.6722
9  401.1   NW       2  6.1492
10 402.1   NW       2  5.0506
11 500.1  NWC       2  6.5625
12 502.1  NWC       2 11.4430
13 601.1  NWR       2  2.8450
14 602.1  NWR       2  5.6558
15 603.1  NWR       2  3.3340
16 604.1  NWR       2  5.0548
17 401.1   NW       3  5.2717
18 402.1   NW       3  3.7337
19 500.1  NWC       3  3.6659
20 502.1  NWC       3  5.9463
21 601.1  NWR       3  2.3356
22 602.1  NWR       3  7.5458
23 603.1  NWR       3  5.0322
24 604.1  NWR       3  4.1381

summary(mgroup <- aov(rl ~ cond * session + Error(subj/(session)), data=mig))

I'm interested in posthoc comparisons between:
various levels of condition (I can get this with TukeyHSD,
pairwise.t.test, or multcomp)
various levels of session (ditto)
the full 6 comparisons (3 sessions by 2 conditions).  that is, I want
to know if NW-session1 is diff from NW-session2, etc.

> tapply(mig$rl,IND=list(mig$cond, mig$session),FUN=mean)
           1       2        3
NW  6.147100 5.59990 4.502700
NWC 6.939700 9.00275 4.806100
NWR 3.827175 4.22240 4.762925

Each of the earlier tests I've tried (TukeyHSD, pairwise.*, and
multcomp) all seem to do only one factor at a time.

Suggestions?

thanks!
greg

(I know my dataset is small, doesn't give appropriate omnibus stats to
run the post-hocs, but I'm currently in testing mode.)
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