[R] Write a function that allows access to columns of a passed dataframe.

[Rui Barradas]

Hello,

You don't need xx <- deparse(substitute(...)), since you are passing the 
data.frame to your function. Just use


myfun <- function(frame,var){

   [...]

   # Nor does this work.
   col <- frame[,yy]
   print(col)
}

myfun(mydf,age)
myfun(frame = mydf, var = age)
[1] 2 3
I can get the name of the dataframe as a text string!
[1] "mydf"
I can get the name of the column as a text string!
[1] "age"
[1] 20 34 43 32 21


Hope this helps,

Rui Barradas



Em 05-12-2016 14:44, John Sorkin escreveu:
> I am trying to write a function which, when passed the name of a dataframe and the name of a column of the dataframe, will allow me to work on the columns of a dataframe. I can not get my code to work. Please see the code below. Any help in getting the function to work would be appreciated.
>
>
>
>
> mydf <- data.frame(id=c(1,2,3,4,5),sex=c("M","M","M","F","F"),age=c(20,34,43,32,21))
> mydf
> class(mydf)
>
>
> myfun <- function(frame,var){
>    call <- match.call()
>    print(call)
>
>
>    indx <- match(c("frame","var"),names(call),nomatch=0)
>    print(indx)
>    if(indx[1]==0) stop("Function called without sufficient arguments!")
>
>
>    cat("I can get the name of the dataframe as a text string!\n")
>    xx <- deparse(substitute(frame))
>    print(xx)
>
>
>    cat("I can get the name of the column as a text string!\n")
>    yy <- deparse(substitute(var))
>    print(yy)
>
>
>    # This does not work.
>    col <- xx[,"yy"]
>
>
>    # Nor does this work.
>    col <- xx[,yy]
>    print(col)
> }
>
>
> myfun(mydf,age)
>
> John David Sorkin M.D., Ph.D.
> Professor of Medicine
> Chief, Biostatistics and Informatics
> University of Maryland School of Medicine Division of Gerontology and Geriatric Medicine
> 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)
>
>
>
>
> John David Sorkin M.D., Ph.D.
> Professor of Medicine
> Chief, Biostatistics and Informatics
> University of Maryland School of Medicine Division of Gerontology and Geriatric Medicine
> 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 ...{{dropped:8}}