[R] using a variable for a column name in a formula

[David Epstein]

lm(height ~ ., data=X)
works fine.

However
nnn <- "height" ;  lm(nnn ~ . ,data=X)
fails

How do I write such a formula, which depends on the value of a string variable like nnn above?

A typical application might be a program that takes a data frame containing only numerical data, and figures out which of the columns can be best predicted from all the other columns.
 
Thanks
David