You can use the createDataPartition() function from the caret package in R to partition a data frame into training and testing sets for model building.
This function uses the following basic syntax:
createDataPartition(y, times = 1, p = 0.5, list = TRUE, …)
- y: vector of outcomes
- times: number of partitions to create
- p: percentage of data to use in training set
- list: whether to store results in list or not
The following example shows how to use this function in practice.
Example: Using createDataPartition() in R
Suppose we have some data frame in R with 1,000 rows that contains information about hours studied by students and their corresponding score on a final exam:
#make this example reproducible set.seed(0) #create data frame df <- data.frame(hours=runif(1000, min=0, max=10), score=runif(1000, min=40, max=100)) #view head of data frame head(df) hours score 1 8.966972 55.93220 2 2.655087 71.84853 3 3.721239 81.09165 4 5.728534 62.99700 5 9.082078 97.29928 6 2.016819 47.10139
Suppose we would like to fit a simple linear regression model that uses hours studied to predict final exam score.
Suppose we would like to train the model on 80% of the rows in the data frame and test it on the remaining 20% of rows.
The following code shows how to use the createDataPartition() function from the caret package to split the data frame into training and testing sets:
library(caret) #partition data frame into training and testing sets train_indices <- createDataPartition(df$score, times=1, p=.8, list=FALSE) #create training set df_train <- df[train_indices , ] #create testing set df_test <- df[-train_indices, ] #view number of rows in each set nrow(df_train)  800 nrow(df_test)  200
We can see that our training dataset contains 800 rows, which represents 80% of the original dataset.
Similarly, we can see that our test dataset contains 200 rows, which represents 20% of the original dataset.
We can also view the first few rows of each set:
#view head of training set head(df_train) hours score 1 8.966972 55.93220 2 2.655087 71.84853 3 3.721239 81.09165 4 5.728534 62.99700 5 9.082078 97.29928 7 8.983897 42.34600 #view head of testing set head(df_test) hours score 6 2.016819 47.10139 12 2.059746 96.67170 18 7.176185 92.61150 23 2.121425 89.17611 24 6.516738 50.47970 25 1.255551 90.58483
We can then proceed to train the regression model using the training set and assess its performance using the testing set.
The following tutorials explain how to use other common functions in R: