r - How to check if .csv-File has a comma or a semicolon as separator?

Question

As the title already says:

I have to read in a lot of .csv-Files automatically. Some have a comma as a delimiter, then i take the command read.csv().

Some have a semicolon as a delimiter, then i take read.csv2().

I want to write a piece of code that recognizes if the .csv-File has a comma or a semicolon as a a delimiter(before i read it) so that I don′t have to change the code everytime. My approach would be something like this:

try to read.csv("xyz")
if error 
read.csv2("xyz")

Is something like that possible? Has somebody done this before? How can i check if there was an error without actually seeing it?

I hope the question is clear. Sorry for my English

Thanks in advance

Answer 1

Here are a few approaches assuming that the only difference among the format of the files is whether the separator is semicolon and the decimal is a comma or the separator is a comma and the decimal is a point.

1) fread As mentioned in the comments fread in data.table package will automatically detect the separator for common separators and then read the file in using the separator it detected. This can also handle certain other changes in format such as automatically detecting whether the file has a header.

2) grepl Look at the first line and see if it has a comma or semicolon and then re-read the file:

L <- readLines("myfile", n = 1)
if (grepl(";", L)) read.csv2("myfile") else read.csv("myfile")

3) count.fields If we can assume that that more than one field exists in each file then if there were one field when sep = ";" we know that semicolon is not the separarator.

L <- readLines("myfile", n = 1)
numfields <- count.fields(textConnection(L), sep = ";")
if (numfields == 1) read.csv("myfile") else read.csv2("myfile")

Update Added (3) and made improvements to all three.