文件错误（文件，“rt”）：无法在 r 中打开连接

Question

I am new to programming.Currently doing R programming in coursera and got this error while doing assignment named "pollutantmean".I searched in forums and stackoverflow,but couldnt able to fix it.Appreciate your help.Thanks.

I got this error :

Error in file(file, "rt") : cannot open the connection In addition: Warning message:
In file(file, "rt") : cannot open file 'NA': No such file or directory

Note: I have a folder "specdata" which is the working directory.This "specdata" has all the 332 csv files.I want to calculate mean for one of the pollutant column named "pollutant" in those files and "directory" is the location of those files."id" is a integer vector mentioning the monitor number.so,here is my code:

 pollutantmean <- function(directory, pollutant, id = 1:332) {            

    files_full <- list.files(directory, full.names = TRUE) 

    dat <- data.frame()

    for (i in id) {
    dat <- rbind(dat, read.csv(files_full[i]))
    }

    mean(dat[, pollutant], na.rm = TRUE)
    }

    pollutantmean("specdata","sulfate",id = 1:10)

Answer 1

As per the error, it seems that list.files is returning empty vector for files names.

list.files returns only file nam inside the directory by default. So in that case, you should set the working directory first, so that read.csv will read the files inside the working directory.

setwd("<directory name>")

Now your function should work fine.