Using a function with apply Error: undefined columns selected
On Apr 7, 2016, at 3:39 PM, John Sorkin <jsorkin at grecc.umaryland.edu> wrote:
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)
At the point where the error is about to occur during the first column being processed, this is what had been printed: Column being processed [1] "newX[, i]" So it should be no surprise that the actual error was: Error in `[.data.frame`(data, , zz) : undefined columns selected It occurred at one of the two points where you tried `data[,zz]` You need to pass colnames(guppy) to fract2 and work with the character values. All of the *apply function pass only values so they do not pass the column names for testing. A possible exception might be the colnames of a vector being avaialble when using apply with an index of 1. --
John David Sorkin M.D., Ph.D.
Snipped
David Winsemius Alameda, CA, USA