See:
http://finzi.psych.upenn.edu/R/Rhelp02a/archive/67474.html
and also the other posts in that thread.
On 10/24/07, Sandy Weisberg <[EMAIL PROTECTED]> wrote:
> I would like to write a function that computes Tukey's 1 df for
> nonadditivity. Here is a simplified version of the function I'd like to
> write: (m is an object created by lm):
>
> tukey.test <- function(m) {
> m1 <- update(m, ~.+I(predict(m)^2))
> summary(m1)$coef
> }
>
> The t-test for the added variable is Tukey's test. This won't work:
>
> data(BOD)
> m1 <- lm(demand~Time,BOD)
> tukey.test(m1)
>
> Error in predict(m) : object "m" not found
>
> This function doesn't work for two reasons:
> 1. The statement m1 <- update(m, ~.+I(predict(m)^2)) can't see 'm' in
> the call to predict.
> 2. If in creating m missing values had been present, then predict(m),
> even if it could be computed, could be of the wrong length.
>
> Can anyone help?
>
>
>
> --
> Sanford Weisberg, [EMAIL PROTECTED]
> Office and mailing address:
> University of Minnesota, School of Statistics
> 312 Ford Hall, 224 Church St. SE, Minneapolis, MN 55455
> 612-625-8355, FAX 612-624-8868
>
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>
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>
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