[R] How to left or right truncate a character string?

[Mark Na]

Hi R-helpers,

I have a character string, for example:

"lm(y ~ X2 + X3 + X4)"

from which I would like to strip off the leading and trailing
quotation marks resulting in this:

lm(y ~ X2 + X3 + X4)


I have tried using gsub() but I can't figure out how to specify the
quotation mark using a regular expression.

Alternatively, I would like a function that lets me delete the leading
(or trailing) X characters, and in this case X=1 (but it could be used
more flexibly to delete several leading or trailing characters).

I would appreciate help with either of these potential solutions (gsub
and regex, or delete leading/trailing characters).

Many thanks!

Mark