pollutantmean <- function(directory = "specdata", pollutant = "sulfate", id =
"001") {
pollutantcount <- 0
pollutantsum <- 0

filetype <- ".csv"
pathswitch <- "."


file_len <- nchar(id)
if (file_len == 1) {
new_id <- paste("00", id, filetype, sep = "")}
else if (file_len == 2) {
new_id <- paste("0", id, filetype, sep = "")}
else
new_id <- paste(id, filetype, sep = "")
new_path <-  file.path(pathswitch,directory, new_id)
new_data <- read.csv(new_path)
pollutantsum <- pollutantsum + sum(new_data[,pollutant], na.rm=TRUE)
pollutantcount <- pollutantcount + length(na.exclude(new_data[,pollutant]))
meanofpollutant <- (pollutantsum / pollutantcount)
print(meanofpollutant)