string formula not evaluated in global environment?

Question

The string formula in the loop throws an error with standardize(), whereas the non-loop versions do not. Environment issue?

library(arm)
set.seed(1)         


        

Answer 1

It is important that the formula is actually substituted in the lm object:

for (i in list(quote(x1), quote(x2))) {
    f <- bquote(y ~ .(i))
    m0 <- eval(bquote(lm(.(f), data=df)))
    m0z <- arm::standardize(m0)
}

Answer 2

A solution is to not use string formulas, but rather to construct a formula from an expression, and evaluate that:

f = eval(bquote(y ~ .(as.name(i))))

This works because f will be constructed in the current environment.

Alternatively, just call as.formula(f) manually instead of passing the naked f to lm; however, I always dislike going the detour via strings. This is an anti-pattern known as stringly typing.