R Load CSV File as data.table (2 Examples)
In this post, you’ll learn loading a CSV file as a data.table and saving a data.table as a CSV file in R programming.
Setting up the Examples
Install and load the data.table package.
install.packages("data.table") # Install & load data.table package library("data.table") |
We use the iris dataset to illustrate the file saving and loading.
data(iris) # Loading iris data set head(iris) # Printing head of data # Sepal.Length Sepal.Width Petal.Length Petal.Width Species # 1 5.1 3.5 1.4 0.2 setosa # 2 4.9 3.0 1.4 0.2 setosa # 3 4.7 3.2 1.3 0.2 setosa # 4 4.6 3.1 1.5 0.2 setosa # 5 5.0 3.6 1.4 0.2 setosa # 6 5.4 3.9 1.7 0.4 setosa |
Define object iris_dt, which is the data.table version of the iris data.
iris_dt <- data.table(data.table::copy(iris)) # Copying data as data.table |
Set a path to a folder of your choice. We use this folder to store the example data in.
path <- "C:/Users/..." # Setting a path to the folder where you want to save the data to |
Example 1: Exporting a data.table as a CSV File
We can export the data iris_dt as a CSV file with the following command.
?write.csv |
write.csv(iris_dt, # Saving data as CSV file file = paste0(path, "iris_csv.csv")) |
For the different options of function write.csv(), take a look at the documentation, which you can open with ?write.csv. For example, the arguments allow for changing the decimal symbol.
Example 2: Importing a CSV File as a data.table
In this example, we read a CSV file as a data.table. For that, we first read the file as a data.frame and then convert it to a data.table with the following lines of code. With class(), we check for the class of the object.
iris_imported <- read.csv(file = paste0(path, "iris_csv.csv")) # Reading the data class(iris_imported) # Getting object class # [1] "data.frame" |
setDT(iris_imported) # Transforming to data.table class(iris_imported) # Getting object class # [1] "data.table" "data.frame" |
Note: This article was created in collaboration with Anna-Lena Wölwer. Anna-Lena is a researcher and programmer who creates tutorials on statistical methodology as well as on the R programming language. You may find more info about Anna-Lena and her other articles on her profile page.