Use substitute: > f <- function(e1, n) substitute(e1^n, list(e1 = e1, n = n[[1]])) > f(expression(x^2+y^2), expression(n)) expression(x^2 + y^2)^n
On Fri, Sep 4, 2009 at 10:22 PM, Turner Rolf<r.tur...@auckland.ac.nz> wrote: > > I am trying to construct a function to which I pass an expression as an > argument. > >From that expression I want to create a somewhat more complicated expression > and then differentiate it using D() or deriv(). > > To give a simple example, I'd like to be able to do something like > > e1 <- expression(x^2 + y^2) > e2 <- some.magic(e1,"n") > > or maybe e2 <- some.magic(e1,expression(n)) > > and get e2 being expression((x^2+y^2)^n). (Whence I can then do D(e2,"x") > and D(e2,"y").) > > Is there any way to accomplish this? > > Thanks. > > cheers, > > Rolf Turner > ###################################################################### > Attention: > This e-mail message is privileged and confidential. If you are not the > intended recipient please delete the message and notify the sender. > Any views or opinions presented are solely those of the author. > > This e-mail has been scanned and cleared by MailMarshal > www.marshalsoftware.com > ###################################################################### > > ______________________________________________ > R-help@r-project.org mailing list > https://stat.ethz.ch/mailman/listinfo/r-help > PLEASE do read the posting guide http://www.R-project.org/posting-guide.html > and provide commented, minimal, self-contained, reproducible code. > ______________________________________________ R-help@r-project.org mailing list https://stat.ethz.ch/mailman/listinfo/r-help PLEASE do read the posting guide http://www.R-project.org/posting-guide.html and provide commented, minimal, self-contained, reproducible code.
