Message-ID: <Pine.LNX.4.31.0212131742220.8041-100000@gannet.stats>
Date: 2002-12-13T18:45:03Z
From: Brian Ripley
Subject: How to get objects from a "formula" specification?
In-Reply-To: <4fc1d4ee8b.4ee8b4fc1d@jhsph.edu>
?model.frame
?model.matrix
`S Programming' by Venables & Ripley (2000).
On Fri, 13 Dec 2002, Ravi Varadhan wrote:
> Hi:
>
> I'd like to get the objects corresponding to the elements in a formula,
> from a data frame. For example, suppose I would like to make a
> function call, such as follows:
>
> myfunc(formula="y ~ x1 + x2 + log(x3)" , data=mydata)
>
> This function will get the vector objects y, x1, x2, and log(x3) from
> the data frame "mydata" to form the design matrix and then perform a
> maximum likelihood estimation of the regression parameters.
>
> My questions is, how do I get the the vector objects y, x1, x2, and
> log(x3),specified the formula, from the data frame "mydata"?
BTW, that's not precisely how formulae in R work.
--
Brian D. Ripley, ripley at stats.ox.ac.uk
Professor of Applied Statistics, http://www.stats.ox.ac.uk/~ripley/
University of Oxford, Tel: +44 1865 272861 (self)
1 South Parks Road, +44 1865 272860 (secr)
Oxford OX1 3TG, UK Fax: +44 1865 272595