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

[John Sorkin]

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) 





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