Is there ever a case that X[,names(X)[4]] would give a different result
than X[,4]?  Or is this just a case of the "the longest distance between
any 2 points is a shortcut"?

Well I guess if X has non-unique names then you might see a difference, but
having a data frame with non-unique names and using the longer version
above is more likely to be asking for trouble than doing anything useful.


On Fri, Oct 4, 2013 at 10:15 AM, John Kane <jrkrideau@inbox.com> wrote:

> X[,names(X)[4]]  works fine  for me.  I had never thought of doing this.
> Neat idea.
>
> John Kane
> Kingston ON Canada
>
>
> > -----Original Message-----
> > From: jimmycloud@gmail.com
> > Sent: Fri, 4 Oct 2013 12:06:50 -0400
> > To: r-help@r-project.org
> > Subject: [R] quote a column of a dataframe by its name
> >
> > Dear All,
> >
> > I have a question, suppose X is a dataframe, with column names as
> > "x1", "x2", "x3", ..... And I would like to use the i-th column by
> > X[,'xi'].
> > But it seems the single quote and double quote are different.
> > So if I run X[, names(X)[i]], it has some error.
> > Please use the below example code
> >
> > X = matrix(rnorm(50),ncol = 5)
> > X = data.frame(X)
> > names(X)=c("x1","x2","x3","x4","x5")
> >
> > #pick the 4-th column
> > X[,'x4']  #working
> > X[,names(X)[4]]  # not working , so how to modify this line?
> >
> > names(X)[4] #  returns "x4"
> > sQuote(names(X)[4])  # returns "'x4'"
> >
> >
> > Best,
> >
> > ______________________________________________
> > R-help@r-project.org 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.
>
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>



-- 
Gregory (Greg) L. Snow Ph.D.
538280@gmail.com

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