Transposing a data.table in R (Example Code)
This post shows how to flip a data.table over its diagonal in the R programming language.
Setting up the Example
Install and load the data.table package.
install.packages("data.table") # Install & load data.table library("data.table") |
Load the built-in iris dataset as an example.
data(iris) # Load iris data set head(iris) # 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 |
Convert the example data into a data.table with function setDT() from the data.table package.
iris_dt <- data.table::copy(iris) # Replicate iris data set setDT(iris_dt) # Convert iris to a data.table head(iris_dt) # Print the head of the 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 |
Example: Get the Transpose of the iris Data
For illustrate how to rotate the iris dataset, we use the first three data rows.
iris_dt_2 <- iris_dt[1:3,] # Reduce the data to the first three rows iris_dt_2 # Print the 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 |
We can transpose the data.table with function transpose() from the data.table package.
iris_dt_2_tr <- transpose(iris_dt_2) # Transpose the data iris_dt_2_tr # Print the data # V1 V2 V3 # 1: 5.1 4.9 4.7 # 2: 3.5 3 3.2 # 3: 1.4 1.4 1.3 # 4: 0.2 0.2 0.2 # 5: setosa setosa setosa |
You can see that the data was rotated along the diagonal line.
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.