On 2011-07-26 01:13, Achim Zeileis wrote:


On Tue, 26 Jul 2011, Lao Meng wrote:

Hi all:
There's a question about glht function.

My data:data_ori,which inclue CD4, GROUP,time.


f_GROUP<-factor(data_ori$GROUP)

f_GROUP is a factor of 3 levels(0,1,2,3)


result<- lme(sqrt(CD4) ~ f_GROUP*time ,random = ~time|ID,data=data_ori)

glht(result, linfct = mcp(f_GROUP="Tukey") )
Error in `[.data.frame`(mf, nhypo[checknm]) : undefined columns selected


I can't find out the reason for Error.

We can't either based on the information you provide. If I set up random
data based on your specification, then everything works fine for me in R
2.13.1 with nlme 3.1-102 and multcomp 1.2-7.

## random data
set.seed(0)
data_ori<- data.frame(
    CD4 = rnorm(100)^2,
    time = runif(100),
    f_GROUP = factor(sample(0:3, 100, replace = TRUE)),
    ID = factor(rep(1:10, each = 10))
)

## model fitting
library("nlme")
result<- lme(sqrt(CD4) ~ f_GROUP * time, random = ~ time | ID,
    data = data_ori)

## multiple comparisons
library("multcomp")
glht(result, linfct = mcp(f_GROUP = "Tukey"))

Everything works ok. glht() just issues an appropriate warning that Tukey
contrasts of f_GROUP might not be what you want in the presence of
interactions.

Yes, but try this:

 set.seed(0)
 data_ori <- data.frame(
    CD4 = rnorm(100)^2,
    time = runif(100),
    GROUP = sample(0:3, 100, replace = TRUE),
    ID = factor(rep(1:10, each = 10))
 )

 f_GROUP<-factor(data_ori$GROUP)
 result <- lme(sqrt(CD4) ~ f_GROUP * time, random = ~ time | ID,
    data = data_ori)
 glht(result, linfct = mcp(f_GROUP = "Tukey"))
 #Error in `[.data.frame`(mf, nhypo[checknm]) : undefined columns
 # selected

(Note that I changed data_ori$f_GROUP to data_ori$GROUP.)

Peter Ehlers



Any help from you are welcome.


Many thanks!

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