[R] How to get objects from a "formula" specification?

[ripley@stats.ox.ac.uk]

?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)
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