[R] quote a column of a dataframe by its name

[John Kane]

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 at gmail.com
> Sent: Fri, 4 Oct 2013 12:06:50 -0400
> To: r-help at 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,
> 
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