R help - Oct 2016 - Error creating named character vectors from column names in data frame.

Hi everyone,

I was hoping someone would explain why this doesn't work.

c("a" = "b") # named character vector
class("a") # character
class("b") # character

c(names(mtcars)[1] = names(mtcars[2]) # error
class(names(mtcars)[1]) # character
class(names(mtcars)[2]) # character


Thanks,
Jorge Cimentada

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I'm sorry, there was a typo. The result is still the same:

c("a" = "b") # named character vector
class("a") # character
class("b") # character

c(names(mtcars)[1] = names(mtcars)[2]) # error
class(names(mtcars)[1]) # character
class(names(mtcars)[2]) # character

Thanks,
Jorge Cimentada

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I think you have R semantics confused. What do you think

c("a" = "b")

means?

Note that:
> c("a" = "b")
  a
"b"
> a
Error: object 'a' not found


And of course:

class("a") # character
class("b") # character

but this has *nothing* to do with the line immediately above it.

Have you gone through any  basic R tutorials? There are many good ones
on the web.

Cheers,
Bert


Bert Gunter

"The trouble with having an open mind is that people keep coming along
and sticking things into it."
-- Opus (aka Berkeley Breathed in his "Bloom County" comic strip )


On Fri, Oct 7, 2016 at 9:06 AM, Jorge Cimentada <cimentadaj at gmail.com>
wrote:
> Hi everyone,
>
> I was hoping someone would explain why this doesn't work.
>
> c("a" = "b") # named character vector
> class("a") # character
> class("b") # character
>
> c(names(mtcars)[1] = names(mtcars[2]) # error
> class(names(mtcars)[1]) # character
> class(names(mtcars)[2]) # character
>
>
> Thanks,
> Jorge Cimentada
>
>         [[alternative HTML version deleted]]
>
> ______________________________________________
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> PLEASE do read the posting guide
http://www.R-project.org/posting-guide.html
> and provide commented, minimal, self-contained, reproducible code.

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.

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