[R] anova
Jason Turner
jasont at indigoindustrial.co.nz
Tue Aug 5 00:03:06 CEST 2003
Peter Dalgaard BSA wrote:
> "Anna H. Pryor" <anna at ptolemy.arc.nasa.gov> writes:
>
>
>>I looked at the Introduction to R and am still confused. Would it be possible
>>to ask a question in which I have three vectors and I want to perform an
>>anova on them. Say A,B, and C. Is there a standard form that I could use in
>>lm to get a model that I could use in anova? Do I need to know more about my
>>problem?
>>
>>I really appreciate any help in this.
>
>
> There are many forms of anova. The type you describe, I presume, is
> data from three separate groups, aka one-way ANOVA. You need to first
> force your data into the parallel-vector layout like this
>
> y <- c(A,B,C)
> group <- factor(rep(1:3,c(7,9,13))) # provided there are 7 elements
> # in A, 9 in B and 13 in C
>
> and then
>
> anova(lm(y~group))
>
> or, for some more options, consider
>
> oneway.test(y~group)
Peter, being modest, didn't mention that he's written a very good book
about R for technical people who aren't statisticians. At fatbrain:
http://search.barnesandnoble.com/textbooks/booksearch/isbnInquiry.asp?isbn=0387954759&TXT=Y&itm=1
If you're not a statistician but are required to use some statistical
methods (such as anova), this is a very helpful book. Most of R's
documentation is aimed at statisticians, so this book fills a gap very
nicely.
Cheers
Jason
--
Indigo Industrial Controls Ltd.
64-21-343-545
jasont at indigoindustrial.co.nz
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