I want to write a function to standardize regression predictors, which
will require me to do some character-string manipulation to parse the
variables in a call to lm() or glm().
For example, consider the call
lm (y ~ female + I(age^2) + female:black + (age + education)*female).
I want to be able to parse this to pick out the input variables
("female", "age", "black", "education"). Then I can transform these as
appropriate (to get "z.female", "z.age", etc), feed them back into the
lm() function, and go from there.
Does anyone know an easy way to pull out the variables? I basically
have to parse out the symbols "+", ":", "*", and " ", but there's also
the problem of handling parentheses and the I() operator.
Thanks!
Andrew
--
Andrew Gelman
Professor, Department of Statistics
Professor, Department of Political Science
[EMAIL PROTECTED]
www.stat.columbia.edu/~gelman
Statistics department office:
Social Work Bldg (Amsterdam Ave at 122 St), Room 1016
212-851-2142
Political Science department office:
International Affairs Bldg (Amsterdam Ave at 118 St), Room 731
212-854-7075
Mailing address:
1255 Amsterdam Ave, Room 1016
Columbia University
New York, NY 10027-5904
212-851-2142
(fax) 212-851-2164
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