hello,
i found it most convenient to use package contrast for planned comparisons
on mixed models.
for instance i have a model with 2 fixed factors, one with 4 levels (stage)
and one with 2 levels (gap) and a nested random factor (site) and i tested
gap within level A of factor stage:
library(contrast)
library(nlme)
m1<-lme(rich ~ stage*gap, random=~1|site,data=richness)
contrast(m1,
a = list(stage="A",gap="0"),
b = list(stage="A",gap="1"))
..this works fine. now i wont to do the same with lmer() because the
response is a count - but this doesn't work with contrast():
library(lme4)
detach(package:nlme)
m2<-lmer(rich ~ stage*gap+(1|site),family=poisson,data=richness)
contrast(m2,
a = list(stage="A",gap="0"),
b = list(stage="A",gap="1"))
Error in UseMethod("contrast") :
no applicable method for 'contrast' applied to an object of class
"mer"
i tried with glht() from multcomp, but was not able to set it up right -
could anyone please help me with how this sort of contrast is produced with
glht()?
thanks for any help,
kay
my data:
richness<-data.frame(list(structure(list(stage = structure(c(1L, 1L, 1L, 1L,
1L, 1L,
1L, 1L, 1L, 1L, 1L, 1L, 1L, 1L, 1L, 1L, 1L, 1L, 1L, 1L, 1L, 1L,
1L, 1L, 1L, 1L, 1L, 1L, 1L, 1L, 1L, 1L, 1L, 1L, 1L, 1L, 1L, 1L,
1L, 1L, 1L, 1L, 1L, 1L, 2L, 2L, 2L, 2L, 2L, 2L, 2L, 2L, 2L, 2L,
2L, 2L, 2L, 2L, 2L, 2L, 2L, 2L, 2L, 2L, 2L, 2L, 2L, 2L, 2L, 2L,
2L, 2L, 2L, 2L, 2L, 2L, 2L, 2L, 2L, 2L, 2L, 2L, 2L, 2L, 2L, 2L,
2L, 2L, 3L, 3L, 3L, 3L, 3L, 3L, 3L, 3L, 3L, 3L, 3L, 3L, 3L, 3L,
3L, 3L, 3L, 3L, 3L, 3L, 3L, 3L, 3L, 3L, 3L, 3L, 3L, 3L, 3L, 3L,
3L, 3L, 3L, 3L, 3L, 3L, 3L, 3L, 3L, 3L, 3L, 3L, 3L, 3L, 3L, 4L,
4L, 4L, 4L, 4L, 4L, 4L, 4L, 4L, 4L, 1L, 1L, 1L, 1L, 1L, 1L, 1L,
1L, 1L, 1L, 1L, 1L, 1L, 1L, 1L, 1L, 1L, 1L, 1L, 1L, 1L, 1L, 1L,
1L, 1L, 1L, 1L, 1L, 1L, 1L, 1L, 1L, 1L, 1L, 1L, 1L, 1L, 1L, 1L,
1L, 1L, 1L, 1L, 1L, 2L, 2L, 2L, 2L, 2L, 2L, 2L, 2L, 2L, 2L, 2L,
2L, 2L, 2L, 2L, 2L, 2L, 2L, 2L, 2L, 2L, 2L, 2L, 2L, 2L, 2L, 2L,
2L, 2L, 2L, 2L, 2L, 2L, 2L, 2L, 2L, 2L, 2L, 2L, 2L, 2L, 2L, 2L,
2L, 3L, 3L, 3L, 3L, 3L, 3L, 3L, 3L, 3L, 3L, 3L, 3L, 3L, 3L, 3L,
3L, 3L, 3L, 3L, 3L, 3L, 3L, 3L, 3L, 3L, 3L, 3L, 3L, 3L, 3L, 3L,
3L, 3L, 3L, 3L, 3L, 3L, 3L, 3L, 3L, 3L, 3L, 3L, 3L, 3L, 4L, 4L,
4L, 4L, 4L, 4L, 4L, 4L, 4L, 4L), .Label = c("A", "B",
"C", "D"
), class = "factor"), site = structure(c(2L, 1L, 1L, 1L, 1L,
2L, 2L, 2L, 3L, 3L, 3L, 3L, 4L, 4L, 4L, 4L, 5L, 6L, 6L, 6L, 6L,
7L, 7L, 7L, 8L, 8L, 8L, 8L, 9L, 9L, 9L, 9L, 10L, 10L, 10L, 10L,
11L, 11L, 11L, 11L, 12L, 12L, 12L, 12L, 13L, 13L, 13L, 14L, 14L,
14L, 14L, 15L, 15L, 15L, 15L, 16L, 16L, 16L, 16L, 17L, 17L, 17L,
17L, 18L, 18L, 19L, 19L, 19L, 19L, 20L, 20L, 20L, 20L, 21L, 21L,
21L, 21L, 22L, 22L, 22L, 22L, 23L, 23L, 23L, 24L, 24L, 24L, 24L,
25L, 25L, 25L, 25L, 26L, 26L, 26L, 26L, 27L, 27L, 27L, 27L, 28L,
28L, 28L, 28L, 29L, 29L, 29L, 30L, 30L, 30L, 30L, 31L, 31L, 32L,
32L, 32L, 32L, 33L, 33L, 33L, 33L, 34L, 34L, 34L, 34L, 35L, 35L,
35L, 35L, 36L, 36L, 36L, 36L, 37L, 37L, 38L, 38L, 38L, 38L, 39L,
39L, 39L, 39L, 2L, 1L, 1L, 1L, 1L, 2L, 2L, 2L, 3L, 3L, 3L, 3L,
4L, 4L, 4L, 4L, 5L, 6L, 6L, 6L, 6L, 7L, 7L, 7L, 8L, 8L, 8L, 8L,
9L, 9L, 9L, 9L, 10L, 10L, 10L, 10L, 11L, 11L, 11L, 11L, 12L,
12L, 12L, 12L, 13L, 13L, 13L, 14L, 14L, 14L, 14L, 15L, 15L, 15L,
15L, 16L, 16L, 16L, 16L, 17L, 17L, 17L, 17L, 18L, 18L, 19L, 19L,
19L, 19L, 20L, 20L, 20L, 20L, 21L, 21L, 21L, 21L, 22L, 22L, 22L,
22L, 23L, 23L, 23L, 24L, 24L, 24L, 24L, 25L, 25L, 25L, 25L, 26L,
26L, 26L, 26L, 27L, 27L, 27L, 27L, 28L, 28L, 28L, 28L, 29L, 29L,
29L, 30L, 30L, 30L, 30L, 31L, 31L, 32L, 32L, 32L, 32L, 33L, 33L,
33L, 33L, 34L, 34L, 34L, 34L, 35L, 35L, 35L, 35L, 36L, 36L, 36L,
36L, 37L, 37L, 38L, 38L, 38L, 38L, 39L, 39L, 39L, 39L), .Label =
c("A11",
"A12", "A14", "A15", "A16",
"A17", "A18", "A19", "A20",
"A5",
"A7", "A8", "B1", "B12",
"B13", "B14", "B15", "B17",
"B18", "B2",
"B4", "B7", "B8", "B9", "C1",
"C10", "C11", "C15", "C17",
"C18",
"C19", "C2", "C20", "C3",
"C4", "C6", "D1", "D4", "D7"),
class = "factor"),
gap = structure(c(1L, 1L, 1L, 1L, 1L, 1L, 1L, 1L, 1L, 1L,
1L, 1L, 1L, 1L, 1L, 1L, 1L, 1L, 1L, 1L, 1L, 1L, 1L, 1L, 1L,
1L, 1L, 1L, 1L, 1L, 1L, 1L, 1L, 1L, 1L, 1L, 1L, 1L, 1L, 1L,
1L, 1L, 1L, 1L, 1L, 1L, 1L, 1L, 1L, 1L, 1L, 1L, 1L, 1L, 1L,
1L, 1L, 1L, 1L, 1L, 1L, 1L, 1L, 1L, 1L, 1L, 1L, 1L, 1L, 1L,
1L, 1L, 1L, 1L, 1L, 1L, 1L, 1L, 1L, 1L, 1L, 1L, 1L, 1L, 1L,
1L, 1L, 1L, 1L, 1L, 1L, 1L, 1L, 1L, 1L, 1L, 1L, 1L, 1L, 1L,
1L, 1L, 1L, 1L, 1L, 1L, 1L, 1L, 1L, 1L, 1L, 1L, 1L, 1L, 1L,
1L, 1L, 1L, 1L, 1L, 1L, 1L, 1L, 1L, 1L, 1L, 1L, 1L, 1L, 1L,
1L, 1L, 1L, 1L, 1L, 1L, 1L, 1L, 1L, 1L, 1L, 1L, 1L, 2L, 2L,
2L, 2L, 2L, 2L, 2L, 2L, 2L, 2L, 2L, 2L, 2L, 2L, 2L, 2L, 2L,
2L, 2L, 2L, 2L, 2L, 2L, 2L, 2L, 2L, 2L, 2L, 2L, 2L, 2L, 2L,
2L, 2L, 2L, 2L, 2L, 2L, 2L, 2L, 2L, 2L, 2L, 2L, 2L, 2L, 2L,
2L, 2L, 2L, 2L, 2L, 2L, 2L, 2L, 2L, 2L, 2L, 2L, 2L, 2L, 2L,
2L, 2L, 2L, 2L, 2L, 2L, 2L, 2L, 2L, 2L, 2L, 2L, 2L, 2L, 2L,
2L, 2L, 2L, 2L, 2L, 2L, 2L, 2L, 2L, 2L, 2L, 2L, 2L, 2L, 2L,
2L, 2L, 2L, 2L, 2L, 2L, 2L, 2L, 2L, 2L, 2L, 2L, 2L, 2L, 2L,
2L, 2L, 2L, 2L, 2L, 2L, 2L, 2L, 2L, 2L, 2L, 2L, 2L, 2L, 2L,
2L, 2L, 2L, 2L, 2L, 2L, 2L, 2L, 2L, 2L, 2L, 2L, 2L, 2L, 2L,
2L, 2L, 2L, 2L, 2L, 2L), .Label = c("0", "1"), class =
"factor"),
rich = c(0L, 2L, 3L, 2L, 2L, 1L, 2L, 1L, 1L, 1L, 1L, 0L,
1L, 3L, 3L, 3L, 1L, 2L, 3L, 7L, 4L, 2L, 1L, 3L, 2L, 2L, 2L,
2L, 3L, 4L, 1L, 1L, 2L, 1L, 3L, 1L, 1L, 2L, 0L, 0L, 3L, 1L,
0L, 1L, 3L, 2L, 3L, 5L, 6L, 7L, 2L, 5L, 8L, 10L, 10L, 9L,
3L, 9L, 6L, 2L, 5L, 1L, 6L, 8L, 7L, 7L, 2L, 6L, 7L, 5L, 3L,
2L, 3L, 9L, 9L, 9L, 9L, 5L, 7L, 4L, 2L, 8L, 4L, 8L, 5L, 8L,
5L, 3L, 7L, 6L, 7L, 8L, 6L, 7L, 5L, 6L, 10L, 10L, 15L, 10L,
11L, 5L, 10L, 6L, 7L, 7L, 10L, 7L, 11L, 6L, 4L, 4L, 6L, 5L,
6L, 5L, 5L, 8L, 5L, 5L, 7L, 5L, 9L, 8L, 6L, 9L, 3L, 4L, 8L,
9L, 7L, 10L, 9L, 9L, 12L, 10L, 12L, 12L, 13L, 11L, 9L, 9L,
9L, 0L, 2L, 1L, 4L, 2L, 2L, 1L, 1L, 1L, 1L, 1L, 1L, 1L, 2L,
2L, 3L, 1L, 7L, 4L, 2L, 4L, 2L, 2L, 3L, 1L, 3L, 1L, 1L, 1L,
2L, 2L, 3L, 2L, 1L, 2L, 1L, 1L, 2L, 2L, 0L, 3L, 2L, 2L, 3L,
1L, 2L, 2L, 4L, 5L, 4L, 5L, 7L, 6L, 4L, 9L, 5L, 2L, 2L, 0L,
3L, 6L, 1L, 4L, 3L, 3L, 4L, 2L, 5L, 7L, 4L, 2L, 1L, 1L, 5L,
4L, 4L, 4L, 1L, 2L, 1L, 2L, 6L, 5L, 10L, 1L, 4L, 4L, 1L,
3L, 5L, 4L, 4L, 4L, 4L, 4L, 3L, 3L, 5L, 9L, 4L, 5L, 6L, 7L,
4L, 5L, 4L, 7L, 4L, 6L, 5L, 2L, 3L, 2L, 6L, 1L, 4L, 5L, 6L,
3L, 5L, 4L, 4L, 3L, 2L, 4L, 1L, 4L, 3L, 4L, 3L, 6L, 2L, 9L,
8L, 10L, 5L, 7L, 10L, 7L, 7L, 4L, 5L, 5L)), .Names = c("stage",
"site", "gap", "rich"), class =
"data.frame", row.names = c(NA,
-286L))))
-----
------------------------
Kay Cichini
Postgraduate student
Institute of Botany
Univ. of Innsbruck
------------------------
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