r - coursera air pollution assignment -

using mac os 10.10.3 rstudio version 0.98.1103

my working directory list of 332 .csv files , set correctly. here's code:

pollutantmean <- function(directory, pollutant, id = 1:332) {   all_files <- list.files(directory, full.names = t)   dat <- data.frame()   for(i in id) {     dat <- rbind(dat, read.csv(all_files[i]))   }   ds <- (dat[, pollutant], na.rm = true)   mean(ds[, pollutant]) } 

part of assignment mean of first 10 numeric values of pollutant. this, used call function (where "spectata" directory 332 .csv files):

pollutantmean(specdata, "nitrate", 1:10) 

the error messages are:

**error in file(file, "rt") : cannot open connection

** in addition: warning message: in file(file, "rt") : cannot open file 'na': no such file or directory

like many students have posed questions here, i’m new programming , r , still distant getting results when calling function. there many questions , answers coursera assignment in stack overflow review of these exchanges hasn't addressed bug in code.

anyone have suggestion how fix bug?

in addition other answers can try this:

all_files <- list.files(directory, pattern="*.csv", full.names = true) 

to avoid select other kind of file.

or strange one

all_files <- paste(directory, "\\", sprintf("%03d", id), ".csv", sep="")