> On Oct 7, 2016, at 10:44 AM, Jorge Cimentada <cimenta...@gmail.com> wrote: > > Hi Bert, > > Yes, I'm aware of the difference between a and "a" but in terms of object > classes I don't see the difference between "a" and names(mtcars)[1]. > They're both strings.
They are not both "strings". One is a character value and the other is an expression that requires two different function evaluations. Inside the call to `c()`, the expressions on either side of an "="-sign are handled differently than they are outside a matching set of function parentheses. I _think_ they are parsed as 'alists', and teh which the ?alist page says the alist()-function does not evaluate the LHS of a pair being formed by the "="-operator. I was, however, not able to find descriptions of this in either The R Language Definition or R Internals. I see Duncan has pointed out that "a" is converted to an R symbol/name as a "courtesy". There is some irony in the fact that the `names` function does not return R names, which are language objects with mode name. -- David > However, for creating a named character vector, this > works: > > c("a" = "b) > > But this doesn't > > c(names(mtcars)[1] = "b") > For example: > > df <- data.frame("a" = 1:5) > c("a" = "b") > c(names(df)[1] = "b") # error > > But > > identical(names(df)[1], "a") > The `identical` function evaluates both its arguments. > That was my initial question. > > [[alternative HTML version deleted]] > > ______________________________________________ > R-help@r-project.org mailing list -- To UNSUBSCRIBE and more, see > 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. David Winsemius Alameda, CA, USA ______________________________________________ R-help@r-project.org mailing list -- To UNSUBSCRIBE and more, see 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.