Merge selected csv files based on name and (calculate means)

Assignment1_Part1.R

pollutantmean <- function(directory, pollutant, id = 1:332) {
        #1, read id csv files and merge into one datafile called data.
        data <- NULL
        for (i in id) {
                count <- sprintf("%03d",i)
                path <- paste(directory,count,".csv",sep="")
                data <- rbind(data, read.csv(path))
        }
        #2, return the mean of the specific pollutant, 
        #with variable precision = 4
        a <- mean(data[,pollutant],na.rm=TRUE)
        print(a,digits=4)
}