[R] What does "rbind(iris[,,1], iris[,,2], iris[,,3])" do?

[Sasha Pustota]

Brian Ripley <ripley at stats.ox.ac.uk> wrote:
> 'iris' in S-PLUS is not the same as 'iris' in R, rather similar to 'iris3'
> in R.

Thank you! This answered all my questions.

> You need the fourth (2002) edition of the book to work with R.
>
> The book does say in many places (including its title) it is about
> 'S-PLUS', but does have on-line complements about the changes needed for R
> of a similar vintage (last updated Dec 2001).
>
> You are trying to use a book written in 1998 on a different system in
> 2006, and you have the audacity to accuse the authors of making errors
> because it does not work.  I look forwards to receiving your apology.

I apologize for supposing that iris is the same in R and Splus (I did
check the index of the book for "iris" but I should have looked
elsewhere) as well as for supposing that the omission of [1:4] was
"probably a typo". My intention was to get help with understanding and
not for a moment was I thinking of accusing the authors of anything.

S

> On Thu, 13 Apr 2006, Sasha Pustota wrote:
>
> > It's in the Venables & Ripley MASS (ed 3) book in the section on
> > principal components.
> > The context is as follows
> >
> >> ir <- rbind(iris[,,1], iris[,,2], iris[,,3])
> >> ir.species <- factor(c(rep("s",50),rep("c",50),rep("v",50)))
> > (then they use brush(ir) which I guess is not an R function)
> >
> > and then
> >
> >> princomp(log(ir[1:4]),cor=T)
> > (there is no [1:4] in the text which is probably a typo)
>
> No, just your error.
>
> >> From what I can see,
> >
> >> iris[,,1]
> >
> > is the same as
> >
> >> iris
> >
> > and "rbind(iris[,,1], iris[,,2], iris[,,3])" duplicates iris 3 times
> > while "mangling" the row index. What happens to the index and what is
> > the purpose of that?
> >
> > I also seem to get the same result with "rbind(iris[,,1], iris[,,1],
> > iris[,,1])". What is the difference with "rbind(iris[,,1], iris[,,2],
> > iris[,,3])"?