How to Use slice in dplyr for Row Selection in R

In dplyr, use slice() to select rows by their position in a data frame or tibble. You provide row numbers or ranges inside slice() to keep only those rows. It is useful for picking specific rows without filtering by values.

Syntax

The basic syntax of slice() is:

• slice(data, rows): Selects rows by their position.
• data: Your data frame or tibble.
• rows: Numeric indices or ranges indicating which rows to keep.

You can use positive numbers to select rows or negative numbers to exclude rows.

r

slice(data, 1:3)  # Select rows 1 to 3
slice(data, c(2, 5))  # Select rows 2 and 5
slice(data, -1)  # Exclude the first row

Example

This example shows how to use slice() to select specific rows from a tibble.

r

library(dplyr)

# Create example data
my_data <- tibble(
  name = c("Alice", "Bob", "Carol", "David", "Eva"),
  age = c(25, 30, 22, 35, 28)
)

# Select rows 2 to 4
selected_rows <- slice(my_data, 2:4)

print(selected_rows)

Output

# A tibble: 3 × 2
  name    age
  <chr> <dbl>
1 Bob      30
2 Carol    22
3 David    35

Common Pitfalls

Common mistakes when using slice() include:

• Using filtering conditions instead of row positions (use filter() for conditions).
• Passing row numbers that are out of range, which causes errors.
• Confusing slice() with slice_head() or slice_tail() which select rows from start or end.

Example of wrong and right usage:

r

library(dplyr)

my_data <- tibble(x = 1:5)

# Wrong: trying to filter rows with condition inside slice (this will cause error)
# slice(my_data, x > 3)  # Incorrect

# Right: use filter for conditions
filter(my_data, x > 3)

# Right: use slice with row positions
slice(my_data, 4:5)

Output

# A tibble: 2 × 1
      x
  <int>
1     4
2     5

Quick Reference

Function	Description	Example Usage
slice()	Select rows by position	slice(data, 1:3)
slice_head()	Select first n rows	slice_head(data, n = 3)
slice_tail()	Select last n rows	slice_tail(data, n = 2)
slice_min()	Select rows with smallest values	slice_min(data, order_by = col)
slice_max()	Select rows with largest values	slice_max(data, order_by = col)

Key Takeaways

Use slice() to select rows by their numeric position in a data frame or tibble.

Provide row numbers or ranges inside slice() to keep specific rows.

Do not use slice() for filtering by values; use filter() instead.

Negative numbers in slice() exclude rows by position.

Check row indices to avoid out-of-range errors.