[R] Cannot subset a specific mean from this function

[Bradley Wolf]

HI,
  I am very new to R (and programming in general) and am taking a class in
it now. I am getting creamed. I want the last part of the function
statement below to give me the mean of the data set of nitrates. When I do
it I get an error statement stating:

Error in pollutantmean$nitrate :
  object of type 'closure' is not subsettable

I am bringing in 332 records. I want the mean of nitrates for 52 of those
records. Any suggestions would be helpful.

pollutantmean <- function(specdata, nitrate,id = 1:332){
  files<-list.files(specdata, full.names = TRUE)
  dat<-data.frame()
  for (i in 280:332)
  dat <- rbind(dat, read.csv(files_full[i]))
}
str(pollutantmean)
mean(pollutantmean$nitrate, na.rm = TRUE)

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