Message-ID: <4fc1d4ee8b.4ee8b4fc1d@jhsph.edu>
Date: 2002-12-13T18:20:03Z
From: Ravi Varadhan
Subject: How to get objects from a "formula" specification?
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"?
thanks for any help,
Ravi.