How to Select Random Rows in R Using dplyr


You can use the following methods to select random rows from a data frame in R using functions from the dplyr package:

Method 1: Select Random Number of Rows

df %>% sample_n(5)

This function randomly selects 5 rows from the data frame.

Method 2: Select Random Fraction of Rows

df %>% sample_frac(.25)

This function randomly selects 25% of all rows from the data frame.

The following examples show how to use each method in practice with the following data frame in R:

#create data frame
df <- data.frame(team=c('A', 'B', 'C', 'D', 'E', 'F', 'G', 'H'),
                 points=c(10, 10, 8, 6, 15, 15, 12, 12),
                 rebounds=c(8, 8, 4, 3, 10, 11, 7, 7))

#view data frame
df

  team points rebounds
1    A     10        8
2    B     10        8
3    C      8        4
4    D      6        3
5    E     15       10
6    F     15       11
7    G     12        7
8    H     12        7

Example 1: Select Random Number of Rows

We can use the following code to randomly select 5 rows from the data frame:

library(dplyr)

#randomly select 5 rows from data frame
df %>% sample_n(5)

  team points rebounds
1    F     15       11
2    A     10        8
3    D      6        3
4    G     12        7
5    B     10        8

Notice that five rows are randomly selected from the data frame.

Example 2: Select Random Fraction of Rows

We can use the following code to randomly select 25% of all rows from the data frame:

library(dplyr)

#randomly select 25% of all rows from data frame
df %>% sample_frac(.25)

  team points rebounds
1    E     15       10
2    G     12        7

Since the original data frame had 8 total values, 25% of 8 is equal to 2.

Thus, two rows are randomly selected from the data frame.

Note: You can find the complete documentation for the sample_n and sample_frac functions in dplyr here.

Additional Resources

The following tutorials explain how to perform other common operations in dplyr:

How to Select Columns by Index Using dplyr
How to Select the First Row by Group Using dplyr
How to Filter by Multiple Conditions Using dplyr
How to Filter Rows that Contain a Certain String Using dplyr

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