[R] Using a function with apply Error: undefined columns selected

[John Sorkin]

I am trying to write a function that can be used to apply to process all the columns of a data.frame. If you will run the code below, you will get the error message undefined columns selected. I hope someone will be able to teach me what I am doing wrong.
Thank you,
John 
 
# create data frame.
guppy
 
fract2 <- function(col,data) {
  cat("Prove we have passed the data frame\n")
  print(data)
  
  # Get the name of the column being processed.
  zz<-deparse(substitute(col))
  cat("Column being processed\n")
  print(zz)
  p<-sum(data[,zz]!="")/length(data[,zz])
  return(p)
}
 
apply(guppy,2,fract2,data=guppy)
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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