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 |
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) |
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 |
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 <- 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 |
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
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