[R] lm on group
Adaikalavan Ramasamy
a.ramasamy at imperial.ac.uk
Sat Jan 23 18:15:53 CET 2010
You can guess by looking at class(g). It is a factor. It is NOT
regressing on the mean of g (i.e. 2.5 and 7.5) and you could have
changed g from (0,5] and (5,10] to A and B with the same results.
Read some books or help(lm) to get an idea of what the outputs mean.
Regards, Adai
newbieRRRRR wrote:
> Hi all,
>
> I have a quick question about lm on group, say I have:
>
> x <- 1:10
> y <- x*3
> buckets <- seq(0, 10, by=5)
> g <- cut(x, buckets)
> summary(lm(y ~ g - 1))
>
> Coefficients:
> Estimate Std. Error t value Pr(>|t|)
> g(0,5] 9.000 2.121 4.243 0.00283 **
> g(5,10] 24.000 2.121 11.314 3.35e-06 ***
>
> What is it doing exactly? I guess the estimate is the mean of the y's
> in each group.
>
> How about other stats.. what do they exactly mean when we do lm on
> groups?
>
>
> Thanks a lot!
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