From: Berwin A Turlach <berwin_at_maths.uwa.edu.au>

Date: Tue 29 Mar 2005 - 09:04:06 GMT

>> In case that a user foolishly specifies a more complicated

* >> formula having not read the help pages. It seemed to me that
*

* >> this was the only construct to figure out which variables are
*

* >> actually appearing in terms of the formula.
*

R-devel@stat.math.ethz.ch mailing list

https://stat.ethz.ch/mailman/listinfo/r-devel Received on Tue Mar 29 19:06:24 2005

Date: Tue 29 Mar 2005 - 09:04:06 GMT

Dear Brian,

>>>>> "BDR" == Prof Brian Ripley <ripley@stats.ox.ac.uk> writes:

[...]

BDR> Still not a description, just two examples.
O.k., I believe that I slowly understand want you want. So in my book
a description of "the job" would be: "that it is allowed to use '.' and
'-' in the formula given to pairs thus allowing pairs.formula".

BDR> Since later on you took a description to be an example, I see
BDR> the confusion.

Just to avoid future confusion, so how does one distinguish a
description from an example, especially if the description is after
the phrase "such as"

BDR> and why you chose such an unusual piece of code to do it?

>> Mmh, I don't think of it as being so unusual, most of it was

* >> gleaned from other R function. Well, I realise that R
** >> programing paradigms change over the years, so I must have
** >> gotten them from quite old routine.
*

BDR> I guess you got it from an S not R function.
Quite possible. Sorry, I can't check since I never had access to S.

BDR> (E.g. what is the prescription for the ordering of terms, and BDR> why do you think the rownames of the factors and the BDR> variables might be in different orders? They are set the BDR> same in the C code.)

>> In case that a user foolishly specifies a more complicated

BDR> Really? Please check what I wrote: `variables' and `rownames BDR> of the factors' are always the same, apart from the response. BDR> Please show an example where you got something different.Sorry, seems to be some misunderstanding here. With 'variables' you mean the "variables" attribute of the object extracted by "mt <- attr(mf, "terms")" in my code? It is well possible that this is always in the same order as the rownames of the factors but I didn't find that in the documentation and I didn't study the C code to write this function. But I take your word for it and in this case I can see how the code could be simplified. Shall I submit a revised version or not bother?

BDR> There are several places where only the allowed form of BDR> formulae is specified in this way. In this case, may I request that this places are better marked than they are at the moment?

BDR> You are not allowed interactions, for example, and it refers
BDR> to `each term'.

Indeed, it states "Each term will give a separate variable in the
pairs plot, so terms should be numeric vectors". So some users might
be surprise that the following works:

> dat <- data.frame(x=rnorm(30), y=rnorm(30), f=rep(c("A","B", "C"), 10)) > pairs(~x+y+f, dat)

Who, but the most arduous student of R help page language would have thought that dat$f is a numeric vector? :-))

BDR> `.' is not documented to work (and used not to). So the question is whether it should remain this way or not. But that is for the R core team to decide and I shall stop my contributions to this thread now.

Cheers,

Berwin

- Full address ============================
Berwin A Turlach Tel.: +61 (8) 6488 3338 (secr)
School of Mathematics and Statistics +61 (8) 6488 3383 (self)
The University of Western Australia FAX : +61 (8) 6488 1028
35 Stirling Highway
Crawley WA 6009 e-mail: berwin@maths.uwa.edu.au
Australia http://www.maths.uwa.edu.au/~berwin

R-devel@stat.math.ethz.ch mailing list

https://stat.ethz.ch/mailman/listinfo/r-devel Received on Tue Mar 29 19:06:24 2005

*
This archive was generated by hypermail 2.1.8
: Mon 24 Oct 2005 - 22:26:32 GMT
*