On Mar 12, 2011, at 10:10 AM, Wensui Liu wrote:
Good morning, dear listers
I am wondering how to do string evaluation such that
model <- glm(Y ~ [STRING], data = mydata) where STRING <- "x1 + x2 +
x3"
It is very doable in other language such as SAS.
Also "very doable" in R. You need to understand that R is a bit more
structured than SAS, which is really just a macro-processor at least
by heritage. Formulas are a language class in R and not just character
vectors, so you need to construct them outside the regression
functions.
STRING <- "x1 + x2 + x3"
form <- formula(paste("Y ~ ", STRING) )
form
# Y ~ x1 + x2 + x3
class(form)
#[1] "formula"
model <- glm(form, data = mydata)
--
David Winsemius, MD
West Hartford, CT
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