[R-sig-ME] mixed effects nested repeated measures MANOVA
Kevin Parsons
kevpar66 at gmail.com
Mon Aug 20 22:08:01 CEST 2012
I have what I think is a fairly complex problem that I hope can be
resolved. I've come close but not quite complete using the 'car'
package but now I've turned my attention to lmer. My experiment
involves looking at 6 traits that were measured twice for time, in two
ecomorphs, under two experimental treatments, with four different
families nested within ecomorphs (2 families per ecomorph). There are
363 individuals
I have come up with the following model for use with lmer:
model2 <- lmer(Y3 ~time*ecomorph*diet*family/ecomorph+(1|individual),
data=data1)
I obtain the following:
Linear mixed model fit by REML
Formula: Y3 ~ time * ecomorph * diet * family/ecomorph + (1 | individual)
Data: data1
AIC BIC logLik deviance REMLdev
-1207 -1124 621.5 -1349 -1243
Random effects:
Groups Name Variance Std.Dev.
fish (Intercept) 0.0012532 0.035401
Residual 0.0081641 0.090355
Number of obs: 726, groups: individuals, 363
Fixed effects:
Estimate Std. Error t value
(Intercept) -0.67115 0.49360 -1.360
time 1.06044 0.30750 3.449
ecomorph 1.18842 0.42141 2.820
diet 0.63752 0.30018 2.124
family 0.75811 0.21545 3.519
time:ecomorph -0.83778 0.26252 -3.191
time:diet -0.47492 0.18700 -2.540
ecomorph:diet -0.60881 0.25211 -2.415
time:family -0.48472 0.13422 -3.611
ecomorph:family -0.49755 0.14252 -3.491
diet:family -0.31653 0.13614 -2.325
time:ecomorph:diet 0.39737 0.15705 2.530
time:ecomorph:family 0.31555 0.08878 3.554
time:diet:family 0.24273 0.08481 2.862
ecomorph:diet:family 0.23655 0.08813 2.684
time:ecomorph:diet:family -0.16362 0.05490 -2.980
While the model runs I'm not feeling comfortable with the results, I
have concerns about the proper F-ratios being used, and as I read more
elsewhere it seems lmer is not taking a wholly multivariate approach?
Someone else has suggested that I calculate coefficients from nested
models that can be found for each response (using either lm, lme,
lmer) . These coefficients can then be concatenated to form a matrix
of coefficients, from which multivariate test statistics can be found.
Could someone please explain how this can be carried out in more
practical terms
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