[R] Can you turn an input into a variable name?

[Bert Gunter]

Well, OK, but do note that strsplit() is vectorized, so

z <- strplit(textlines)  ## provides a list of splits for each line

would be faster for large files.

However, to add to what Jeff said, it is hard for me to see how your
approach will not lead to problems. For example, what if there are several
"age = xxx" lines in the file; or variable number of spaces between the "="
and the left and right sides; etc., which would mean that your "split"
string might need to be a regex that can handle variable numbers of spaces.
In general, keeping such information in a single suitable data structure
rather than having separate symbols (variable names) for each line seems to
me -- in my vast ignorance of your situation!!, so caveat emptor -- to be a
more robust approach.

But anyway ....

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 4, 2019 at 4:11 AM Jim Lemon via R-help <r-help using r-project.org>
wrote:

> Hi April,
> Try this:
>
> # this could be done from a file
> textlines<-read.table(text="color=green
>  shape=circle
>  age=17
>  name=Jim",
>  stringsAsFactors=FALSE)
> for(i in 1:length(textlines)) {
>  nextline<-unlist(strsplit(textlines[i,1],"="))
>  assign(nextline[1],nextline[2])
> }
> color
> [1] "green"
> shape
> [1] "circle"
> age
> [1] "17"
> name
> [1] "Jim"
>
> Jim
>
> On Fri, Oct 4, 2019 at 4:59 PM April Ettington <aprilettington using gmail.com>
> wrote:
> >
> > Let's say I am parsing a file with a list of parameters followed by an
> > equal sign, and their corresponding values, eg:
> >
> > color=green
> > shape=circle
> >
> > and I want to use this information to create a variable called color with
> > the value 'green' and a variable shape with the value 'circle'.
> However, I
> > also want my code to be able to do this *when it doesn't know up front
> what
> > the parameter names will be.  *So, if the file also included "age=7", it
> > should still make a variable called age with the value '7', even though
> > 'age' doesn't specifically appear anywhere in my code.  Is there a way to
> > do this?
> >
> > Thank you,
> > April
> >
> >         [[alternative HTML version deleted]]
> >
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>
> ______________________________________________
> R-help using 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.
>

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