On Fri, 18 Dec 2009, Achim Zeileis wrote:
On Fri, 18 Dec 2009, chrischizinski wrote:
Just in case anyone ever has similar issues, it appears that 'glht' does
not work without an intercept.
That is not precise enough to be useful. I've had a look again and appears to
be the case that mcp() (or rather the internal function mcp2matrix) does not
work for models where there are multiple factors but no intercept.
As the posting guide asks us to do, I have (1) provided a _reproducible_
example below, and (2) included the maintainer of the package in the posting.
Torsten, it would be great if you could have a look.
Achim and Chris,
thanks for spotting this problem. The bug is now fixed in multcomp
1.1-3 available from R-forge.
Torsten
Best,
Z
## package
library("multcomp")
## various models with and without intercept
m1a <- lm(breaks ~ tension, data = warpbreaks)
m1b <- lm(breaks ~ 0 + tension, data = warpbreaks)
m2a <- lm(breaks ~ wool + tension, data = warpbreaks)
m2b <- lm(breaks ~ 0 + wool + tension, data = warpbreaks)
## these two are equivalent: one factor with/without intercept
summary(glht(m1a, linfct = mcp(tension = "Tukey")))
summary(glht(m1b, linfct = mcp(tension = "Tukey")))
## these two should be equivalent: two factors with/without intercept
## but the latter fails
summary(glht(m2a, linfct = mcp(tension = "Tukey")))
summary(glht(m2b, linfct = mcp(tension = "Tukey")))
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