Error in file(file, “rt”) : cannot open the connection

问题

I'm new to R, and after researching this error extensively, I'm still not able to find a solution for it. Here's the code. I've checked my working directory, and made sure the files are in the right directory. Appreciate it. Thanks

pollutantmean <- function(directory, pollutant = "nitrate", id= 1:332)            
{                 if(grep("specdata",directory) ==1) 
            {
                    directory <- ("./specdata")
            }
            mean_polldata <- c()
            specdatafiles <- as.character(list.files(directory))
            specdatapaths <- paste(directory, specdatafiles, sep="")
                            for(i in id) 
                    {
                    curr_file <- read.csv(specdatapaths[i], header=T, sep=",")
                    head(curr_file)
                    pollutant
                    remove_na <- curr_file[!is.na(curr_file[, pollutant]), pollutant]
                    mean_polldata <- c(mean_polldata, remove_na)
                    }
            {
                    mean_results <- mean(mean_polldata)
                    return(round(mean_results, 3))
            }
}

The error I'm getting is below:

Error in file(file, "rt") : cannot open the connection

file(file, "rt")

read.table(file = file, header = header, sep = sep, quote = quote, 
    dec = dec, fill = fill, comment.char = comment.char, ...)

read.csv(specdatapaths[i], header = T, sep = ",")

pollutantmean3("specdata", "sulfate", 1:10)

In addition: Warning message:
In file(file, "rt") :
  cannot open file './specdata001.csv': No such file or directory

回答1:

You need to change directory <- ("./specdata") to directory <- ("./specdata/")

Relative to your current working directory, you are looking for the file 001.csv, which is in your specdata directory.

This question is nearly impossible to answer without any context, since you have not provided us with the structure of your working directory here. Fortunately for you, I have already taken R Programming on Coursera, so I already did this homework question.

回答2:

Set your working directory one level/folder higher. For example, if it is already set as:

setwd("C:/Users/Z/Desktop/Files/RStudio/Coursera/specdata")

go up one level back and set it as:

setwd("C:/Users/Z/Desktop/Files/RStudio/Coursera")

In other words, do not make "specdata" folder as your working directory.

回答3:

I just spent a lot of time trying to understand what was wrong on my code too...

And it seems to be simple if you are using windows.

When you name your file "blabla.txt" then windows name it "blabla.txt.txt"... That's the same with .CSV files so windows create a file named "001.csv.csv" if you called it "001.csv"

So, when you create your .csv file, just rename it "001" and open it in R using read.table("/absolute/path/of/directory/with/required/001.csv")

It works for me.

回答4:

The reason why you see this error I guess is because RStudio lost the path of your working directory.

(1) Go to session...

(2) Set working directory...

(3) Choose directory...

--> Then you can see a window pops up.

--> Choose the folder where you store your data.

This is the way without any code that you change your working directory. Hope this can help you.

回答5:

If running on Windows try running R or R Studio as administrator to avoid Windows OS file system constraints.

回答6:

Use setwd() to change to appropriate directory. Use only filename to access any file in the working directory. Navigate a folder above by using "../<filename>".

回答7:

close your R studio and run it again as an administrator. That did the magic for me. Hope it works for you and anyone going through this too.

回答8:

One better check that can be done if you get such error while accessing a file is to use the file.exists("file_path/file_name") function. This function will return TRUE if the file is existing and accessible, else False.

回答9:

I got this same error message and fixed it in the easiest way I could. I put my .csv file into a file folder on my desktop, opened desktop in the window next to console on RStudio, and then opened my file there, and checked the box next to my .csv file, then I used the "more" pull down menu at the top of this window to set this as my working directory...probably the easiest thing for SUPER beginners like me :)

回答10:

This error also occurs when you try to use the result of getwd() directly in the path. The problem is the missingness of the "/" at the end. Try the following code:

projectFolder <- paste(getwd(), "/", sep = '')

The paste() is to concatenate the forward slash at the end.

回答11:

I got my R code file from a friend and was not able to run read.csv command but If I copy the same command(read.csv ) to a new R script file, it ran fine.

Below command was not running in R code file shared by my friend, working directory,file name etc were all correct because If I created a new R script file and ran below command ,it worked.

           df <- read.csv("file.csv",header=TRUE,stringsAsFactors = FALSE,strip.white = 
           TRUE,sep = ',')

issue/resolution: I right clicked the R code file and unblocked the file and click save button and issue got resolved. I your R code file is in Downloads folder in windows , then move to some other folder.

回答12:

I had a same issue .I removed the extension from the file name.Example my file name was saved as xyz. csv. i saved it as xyz.

回答13:

Got this error and found that RStudio on my Windows machine try to use \ as escape symbol, so had to replace it with \\ to deal with it.

Try file.exists function with your path, e.g.:

file.exists("D:\\R\\path_to_file.csv")

回答14:

Error in file(file, "rt")

Created a .r file and saved it in Desktop together with a sample_10000.csv file.

Once trying to read it

heisenberg <- read.csv(file="sample_100000.csv")

was getting the same error as you

heisenberg <- read.csv(file="sample_10000") Error in file(file, "rt") : cannot open the connection In addition: Warning message: In file(file, "rt") : cannot open file 'sample_10000': No such file or directory

I knew at least two ways to fix this, one using the absolute path and the other changing the working directory.

Absolute path

I fixed it adding the absolute path to the file, more precisely

heisenberg <- read.csv(file="C:/Users/tiago/Desktop/sample_100000.csv")

Working directory

This error shows up because RStudio has a specific working directory defined which isn't necessarily the place the .r file is at.

So, to fix using this approach I've gone to Session > Set Working Directory > Chose Directory (CTRL + Shift + H) and selected Desktop, where the .csv file was at. That way running the following command also worked

heisenberg <- read.csv(file="sample_100000.csv")

来源：https://stackoverflow.com/questions/27466317/error-in-filefile-rt-cannot-open-the-connection

标签

csv