[R] writing a function that will refer to the elements of a dataframe much as is done by lm

[John Sorkin]

I am trying to learn how  to write R functions (really to program in R). I want to write a function that will allow me to refer to the elements of a data frame by column name, much as is done in lm. I can't seem to get the syntax correct. I want the function to print the elements of data2[,"Mo6MONO"]
 
data2 <- data.frame(POSTHHMONO=c(1,2,3,4),Mo6MON=c(10,11,12,13))
data2
doit<- function(pre,post,data) {
  element <- deparse(substitute(pre))
  print(element)
  frame <- deparse(substitute(data))
  print(frame)
  print(frame$element)
}
doit(Mo6MONO,POSTHHMONO,data2)
 
results of running function:
Browse[1]> doit(Mo6MONO,POSTHHMONO,data2)
[1] "Mo6MONO"
[1] "data2"
Error during wrapup: $ operator is invalid for atomic vectors

 
 
I have looked at lm, but don't understand the syntax, and have tried to run lm so as to learn the syntax by just don't understand . . . .
 
HELP
 
Thanks 
John
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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