On 07/10/2016 1:44 PM, Jorge Cimentada 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. 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")
That was my initial question.
It's a parser issue. The parser is looking for a name before the equal
sign; it finds a string literal, and just to be nice, treats it as a
name. But it never evaluates it as an expression; evaluation happens later.
The parser would be simpler (and apparently less confusing) if it just
refused to accept "a" where a name is needed, but at the time this was
written, there was no other way to express a name that was syntactically
a name, e.g. "bad name". Later the `bad name` notation was added, and
it makes more sense to use that.
If you really want the result you expected, you can get it this way:
structure("b", names = names(df)[1])
Duncan Murdoch
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