Here is an alternaive approach that is closer to that used by lm and friends.
> df <- data.frame(x=1:10,y=11:20)
> test <- function(col, dat) eval(substitute(col), envir = dat)
> test(x, df)
[1] 1 2 3 4 5 6 7 8 9 10
> test(y, df)
[1] 11 12 13 14 15 16 17 18 19 20
>
There is a slight added bonus this way
> test(x+y+1, df)
[1] 13 15 17 19 21 23 25 27 29 31
>
(Well, I did say 'slight'.)
Bill Venables.
________________________________________
From: r-help-boun...@r-project.org [r-help-boun...@r-project.org] On Behalf Of
David Winsemius [dwinsem...@comcast.net]
Sent: 30 December 2010 10:44
To: John Sorkin
Cc: r-help@r-project.org
Subject: Re: [R] access a column of a dataframe without qualifying the name
of the column
On Dec 29, 2010, at 7:11 PM, John Sorkin wrote:
> I am trying to write a function that will access a column of a data
> frame without having to qualify the name of the data frame column as
> long as the name of the dataframe is passed to the function. As can
> be seen from the code below, my function is not working:
Not sure what the verb "qualify" means in programming. Quoting?
>
> df <- data.frame(x=1:10,y=11:20)
> df
>
> test <- function(column,data) {
> print(data$column)
> }
>
> test(x,df)
>
> I am trying to model my function after the way that lm works where
> one needs not qualify column names, i.e.
> df <- data.frame(x=1:10,y=11:20)
> test <- function(column,dat) { print(colname <-
deparse(substitute(column)))
+ dat[[colname]]
+ }
>
> test(x,df)
[1] "x"
[1] 1 2 3 4 5 6 7 8 9 10
>
--
David.
>
>
> fit1<- lm(y~x,data=df)
>
>
> John David Sorkin M.D., Ph.D.
> Chief, Biostatistics and Informatics
> University of Maryland School of Medicine Division of Gerontology
> Baltimore VA Medical Center
> 10 North Greene Street
> GRECC (BT/18/GR)
> Baltimore, MD 21201-1524
> (Phone) 410-605-7119
> (Fax) 410-605-7913 (Please call phone number above prior to faxing)
>
> Confidentiality Statement:
> This email message, including any attachments, is for th...{{dropped:
> 6}}
>
> ______________________________________________
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> PLEASE do read the posting guide http://www.R-project.org/posting-guide.html
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David Winsemius, MD
West Hartford, CT
______________________________________________
R-help@r-project.org mailing list
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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.
______________________________________________
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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.
