Hi,
I've looked into ways of implementing this procedure, i.e. repeating the
two-way ANOVA many times, scrambling the order of cases across the
treatments, to produce a distribution of F ratios for each effect. This
seemed a job for the 'boot' package. However, I'm not sure I'm doing an
actual randomization test, as opposed to a bootstrap here. This is how
I've coded the test (using the poisons data):
---<---------------cut here---------------start-------------->---
require(boot)
"boot.lm" <- function(data, i)
{
mod <- lm(time ~ treat * poison, data=data[i, ])
anova(mod)["F value"][[1]][-4] # the F ratios for each effect
}
poisons.boot <- boot(poisons, boot.lm, R=1000, sim="permutation")
---<---------------cut here---------------end---------------->---
Is this the right way to ask for a randomization test using 'boot'?
Thanks in advance.
Cheers,
--
Seb
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