How to get objects from a "formula" specification?
?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