1 Read or Import Data from CSV Files in R

Download testdata.csv file.

One of the most common file formats is the comma-separated values file which uses commas to separate the fields.

To read or import CSV or .csv files in R, after setting the working directory to the folder containing the file, use the line of code below:

If your data does not have header, set the header = FALSE.

read.csv(file = "testdata.csv", header = TRUE)

Without setting the working directory, you can use the full file path to read the CSV or .csv file:

read.csv("C:/Users/Public/Statscodes/Rdata/read-files/testdata.csv", header = TRUE)

CSV File Read in R

If your data uses a comma as decimal point and a semicolon as field separator, then use the read.csv2() function instead of read.csv() which is for cases where the data uses a period as decimal point and a comma as field separator.

A cleaner way to read or import files and work with them in R is to assign names to objects. The name "results" will be assigned to the dataframe object below.

results = read.csv("testdata.csv", header = TRUE)

Then the dataframe can be viewed by calling the object:

results

Image 2 of CSV File Read in R

2 Write or Export Data to CSV Files in R

The dataframe named dtfrm will be used:

dtfrm = data.frame(Group = c("A", "B", "B", "C", "D"), 
                   ID = c("A02", "B12", "B15", "C04", "D07"), 
                   Score = c(9, 8, 8, 10, 7), 
                   Position = c(2, 3, 3, 1, 5))
dtfrm

  Group  ID Score Position
1     A A02     9        2
2     B B12     8        3
3     B B15     8        3
4     C C04    10        1
5     D D07     7        5

To write or export to CSV or .csv files in R to the working directory, use the line of code below:

write.csv(dtfrm, file = "outdata.csv")

Or specify the full file path using the location you want to save it:

write.csv(dtfrm, file = "C:/Users/Public/Statscodes/Rdata/write-files/outdata.csv")

The output should look like this in Excel:

CSV Output Written in R

To remove the row numbers on the first column, set row.names = FALSE as shown below.

write.csv(dtfrm, file = "outdata2.csv", row.names = FALSE)

Or specify a full file path:

write.csv(dtfrm, file = "C:/Users/Public/Statscodes/Rdata/write-files/outdata2.csv", row.names = FALSE)

The output should look like this in Excel:

CSV Output Without Row Numbers Written in R

If you want your data to use a comma as decimal point and a semicolon as field separator, then use the write.csv2() function instead of write.csv() which is for cases where you want the data to use a period as decimal point and a comma as field separator.