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

Jie jimmycloud at gmail.com
Fri Oct 4 18:06:50 CEST 2013

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)

#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'"


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