Splitting Data into Training & Testing Sets in R (Example Code)

In this article you’ll learn how to divide a data frame into training and testing data sets in the R programming language.

Creating Example Data

set.seed(1043857)                                         # Creating example data
df_all <- data.frame(x = round(runif(100), 2),
                     y = round(runif(100), 2),
                     z = sample(letters, 100, replace = TRUE))
head(df_all)                                              # Head of example data
#      x    y z
# 1 0.83 0.67 g
# 2 0.17 0.88 x
# 3 0.88 0.21 m
# 4 0.15 0.43 h
# 5 0.74 0.29 r
# 6 0.80 0.11 k

Example: Creating Train & Test Data with sample Function

ind_split <- sample(c(rep("train", 0.75 * nrow(df_all)),  # Create dummy for splitting
                      rep("test", 0.25 * nrow(df_all))))  # 75% train; 25% test data
df_train <- df_all[ind_split == "train", ]                # Creating train data set
head(df_train)                                            # Head of train data
#      x    y z
# 1 0.83 0.67 g
# 2 0.17 0.88 x
# 3 0.88 0.21 m
# 4 0.15 0.43 h
# 5 0.74 0.29 r
# 6 0.80 0.11 k
df_test <- df_all[ind_split == "test", ]                  # Creating test data set
head(df_test)                                             # Head of test data
#       x    y z
# 7  0.86 0.58 q
# 12 0.31 0.24 f
# 17 0.43 0.89 i
# 20 0.64 0.03 b
# 26 0.30 0.48 o
# 27 0.83 0.04 c

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