Just need a bit more work: R> f <- function(x) exists(deparse(substitute(x))) R> f(y) [1] FALSE R> y <- 1 R> f(y) [1] TRUE R> f(z) [1] FALSE
Andy From: Talbot Katz > > Hi, Andy. > > Thank you for the quick response! Unfortunately, none of > these are exactly > what I'm looking for. I'm looking for the following: > Suppose object y > exists and object z does not exist. If I pass y as the value of the > argument to my function, I want to be able to verify, inside > my function, > the existence of y; similarly, if I pass z as the value of > the argument, I > want to be able to see, inside the function, that z doesn't exist. > > The missing function just checks whether the argument is > missing; in my > case, the argument is not missing, but the object may not > exist. And the > way you use the exists function inside the user-defined > function doesn't > test the argument to the user-defined function, it's just > hard-coded for the > object y. So I'm sorry if I wasn't clear before, and I hope > this is clear > now. Perhaps what I'm attempting to do is unavailable > because it's a bad > programming paradigm. But even an explanation if that's the > case would be > appreciated. > > -- TMK -- > 212-460-5430 home > 917-656-5351 cell > > > > >From: "Liaw, Andy" <[EMAIL PROTECTED]> > >To: "Talbot Katz" <[EMAIL PROTECTED]>,r-help@stat.math.ethz.ch > >Subject: RE: [R] Testing for existence inside a function [Broadcast] > >Date: Tue, 15 May 2007 11:03:12 -0400 > > > >Not sure which one you want, but the following should cover it: > > > >R> f <- function(x) c(x=missing(x), y=exists("y")) > >R> f(1) > > x y > >FALSE FALSE > >R> f() > > x y > > TRUE FALSE > >R> y <- 1 > >R> f() > > x y > >TRUE TRUE > >R> f(1) > > x y > >FALSE TRUE > > > >Andy > > > >From: Talbot Katz > > > > > > Hi. > > > > > > I'm having trouble testing for existence of an object inside > > > a function. > > > > > > Suppose I have a function: > > > > > > f<-function(x){ > > > ... > > > } > > > > > > and I call it with argument y: > > > > > > f(y) > > > > > > I'd like to check inside the function whether argument y > > > exists. Is this > > > possible, or do I have to either check outside the function > > > or pass the name > > > of the argument as a separate argument? > > > > > > If I do exists(x) or exists(eval(x)) inside the function and > > > y does not > > > exist, it generates an error message. If I do exists("x") it > > > says that x > > > exists even if y does not. If I had a separate argument to > > > hold the text > > > string "y" then I could check that. But is it possible > to check the > > > existence of the argument inside the function without passing > > > its name as a > > > separate argument? > > > > > > Thanks! > > > > > > -- TMK -- > > > 212-460-5430 home > > > 917-656-5351 cell > > > > > > ______________________________________________ > > > R-help@stat.math.ethz.ch 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. > > > > > > > > > > > > > > >------------------------------------------------------------- > ----------------- > >Notice: This e-mail message, together with any attachments, contains > >information of Merck & Co., Inc. (One Merck Drive, > Whitehouse Station, > >New Jersey, USA 08889), and/or its affiliates (which may be known > >outside the United States as Merck Frosst, Merck Sharp & Dohme or MSD > >and in Japan, as Banyu - direct contact information for affiliates is > >available at http://www.merck.com/contact/contacts.html) that may be > >confidential, proprietary copyrighted and/or legally > privileged. It is > >intended solely for the use of the individual or entity named on this > >message. If you are not the intended recipient, and have > received this > >message in error, please notify us immediately by reply > e-mail and then > >delete it from your system. > > > >------------------------------------------------------------- > ----------------- > > > > ------------------------------------------------------------------------------ Notice: This e-mail message, together with any attachments,...{{dropped}} ______________________________________________ R-help@stat.math.ethz.ch 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.