On Fri, 1 Apr 2005, Christoph Buser wrote:
> Hi
>
> I used the simtest function from the package multcomp. When
> using simtest with an lm object, it seems to depend on the order
> of the variables in the formula. See the code for an example:
>
> library(multcomp)
> set.seed(1)
> # response
> y <- rnorm(21)
> # one factor
> f1 <- factor(c(rep(c("A", "B", "C"), 7)))
> # and one continuous covariable
> x <- rnorm(21)
> testdata <- cbind(as.data.frame(y), f1, x)
>
> # the same model, just change the order in the formula
> reg1 <- lm(y ~ x + f1, data=testdata)
> reg2 <- lm(y ~ f1 + x, data=testdata)
> summary(simtest(reg1))
> > Coefficients:
> > Estimate t value Std.Err. p raw p Bonf p adj
> > (Intercept) 0.427 -1.670 0.347 0.113 0.453 0.307
> > x 0.295 -0.599 0.256 0.557 1.000 0.848
> > f1B 0.204 -0.406 0.503 0.690 1.000 0.866
> > f1C 0.089 -0.255 0.493 0.802 1.000 0.866
> summary(simtest(reg2))
> > Coefficients:
> > Estimate t value Std.Err. p raw p Bonf p adj
> > (Intercept) 0.427 -1.670 0.347 0.113 0.453 0.307
> > f1B 0.295 -0.599 0.503 0.557 1.000 0.848
> > f1C 0.204 -0.406 0.493 0.690 1.000 0.866
> > x 0.089 -0.255 0.256 0.802 1.000 0.866
>
> The tabular is fix, but the names of the variables are
> permutated, maybe a bug in extracting the formula from the lm
> object.
> You can avoid the problem by using a formula instead of an lm
> object, but in the help is mentioned that simtest works with an
> lm object, too.
you are right, thanks for the hint!
Torsten
>
>
> Regards,
>
> Christoph Buser
>
> --------------------------------------------------------------
> Christoph Buser <[EMAIL PROTECTED]>
> Seminar fuer Statistik, LEO C11
> ETH (Federal Inst. Technology) 8092 Zurich SWITZERLAND
> phone: x-41-1-632-5414 fax: 632-1228
> http://stat.ethz.ch/~buser/
> --------------------------------------------------------------
>
>
______________________________________________
R-devel@stat.math.ethz.ch mailing list
https://stat.ethz.ch/mailman/listinfo/r-devel
