R How to Read Only Certain Variables of Data Frame (Example Code)

In this article, I’ll show how to import a selected set of columns when reading the data in the R programming language.

Example Data

data(iris)                                                           # Iris data set as example data frame
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
write.csv(iris,                                                      # Write iris data set to folder
          "C:/Users/Joach/Desktop/My Folder/iris.csv",
          row.names = FALSE)

Example: Apply fread Function of data.table Package to Read Certain Columns of Data Frame

install.packages("data.table")                                       # Install data.table package
library("data.table")                                                # Load data.table package
iris_selected <- fread("C:/Users/Joach/Desktop/My Folder/iris.csv",  # Import specific variables
                       select = c("Sepal.Length", "Petal.Length", "Species"))
head(iris_selected)                                                  # Head of imported data table
#    Sepal.Length Petal.Length Species
# 1:          5.1          1.4  setosa
# 2:          4.9          1.4  setosa
# 3:          4.7          1.3  setosa
# 4:          4.6          1.5  setosa
# 5:          5.0          1.4  setosa
# 6:          5.4          1.7  setosa
iris_selected_df <- as.data.frame(iris_selected)                     # Convert data.table to data.frame format
head(iris_selected_df)                                               # Head of final data.frame
#   Sepal.Length Petal.Length Species
# 1          5.1          1.4  setosa
# 2          4.9          1.4  setosa
# 3          4.7          1.3  setosa
# 4          4.6          1.5  setosa
# 5          5.0          1.4  setosa
# 6          5.4          1.7  setosa

Related Articles

In addition, you might read the related articles on this website.

Leave a Reply

Your email address will not be published. Required fields are marked *

Fill out this field
Fill out this field
Please enter a valid email address.
You need to agree with the terms to proceed

Menu
Top