[R] reading lmer table
Nicola Spotorno
nicola.spotorno at isc.cnrs.fr
Wed Aug 18 10:50:06 CEST 2010
Dear all,
I'm quite new in R and especially with linear mixed effects models and
I'm not completely sure to read the lmer table in the right way.
for example:
head(march.f)
fam subjID Cond Code reg total first
second log.total log.second cat
3 f 30 an fDan1 3 1.2304688 0.6679688 0.56250000
0.20739519 0.44628710 f
7 f 30 an fDan2 3 0.9414062 0.9414062 0.00000000
-0.06038051 0.00000000 f
11 f 30 an fDan3 3 0.4179688 0.4179688 0.00000000
-0.87234861 0.00000000 f
15 f 30 an fDan4 3 0.6015625 0.3906250 0.21093750
-0.50822484 0.19139485 f
19 f 30 an fDan5 3 1.5625000 1.4726562 0.08984375
0.44628710 0.08603434 f
23 f 30 an fDan6 3 0.3632812 0.2968750 0.06640625
-1.01257795 0.06429435 f
m7 <- lmer(log.second ~ Cond + cat + (1|subjID) + (1|Code), data = march.f)
> summary(m7)
Linear mixed model fit by REML
Formula: log.second ~ Cond + cat + (1 | subjID) + (1 | Code)
Data: march.f
AIC BIC logLik deviance REMLdev
279.6 312.9 -132.8 243.2 265.6
Random effects:
Groups Name Variance Std.Dev.
Code (Intercept) 0.0067216 0.081986
subjID (Intercept) 0.0116881 0.108111
Residual 0.0677396 0.260268
Number of obs: 860, groups: Code, 143; subjID, 38
Fixed effects:
Estimate Std. Error t value
(Intercept) 0.32217 0.02888 11.154
Condle -0.09536 0.02915 -3.271
Condme -0.12683 0.02840 -4.465
catb -0.05677 0.02361 -2.405
Correlation of Fixed Effects:
(Intr) Condle Condme
Condle -0.493
Condme -0.498 0.498
catb -0.357 0.000 -0.041
As we can see in the formula in this model I used 2 predictors as fixed
factor: 'Cond' e 'cat'. Cond has 3 levels ('an', 'le', 'me') while
'cat' has 2 levels ('b', 'f')
My problems start in the 'fixed effects' table:
in my case the intercept is the condition with 'Cond = an' and
'cat=f'; what about the fourth line of the table ('catb')? does it show
the global effect of the skip from level 'f' to level 'b' of the
predictor 'cat' regardless predictor 'Cond' or the effect of the skip
from the intercept ('Cond = an' and 'cat=f') to the condition 'Cond =
an' and 'cat=b'? In few word: does this row indicate a global effect of
the predictor 'cat' or a more specific passage?
Please help me!
Thanks in advance,
Nicola
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