substring()

substring(text, first, last = .Machine$integer.max)

substring() extracts or replaces substrings from character vectors using start and stop positions. It extends substr() with more flexible indexing and can be used on the left-hand side of assignments for in-place modification.

Syntax

substring(text, first, last = .Machine$integer.max)

Parameters

Parameter	Type	Default	Description
text	character	—	A character vector
first	integer	—	Starting position (1-indexed)
last	integer	.Machine$integer.max	Ending position (defaults to end of string)

Examples

Basic usage

x <- "Hello World"

substring(x, 1, 5)
# [1] "Hello"

substring(x, 7)
# [1] "World"

# Using negative indices (from end)
substring(x, -4)
# [1] "World"

Replacing substrings

x <- "Hello World"
substring(x, 1, 5) <- "Hi"
x
# [1] "Hi World"

Working with vectors

words <- c("apple", "banana", "cherry")
substring(words, 2, 4)
# [1] "ppl" "ana" "her"

# From position to end
substring(words, 3)
# [1] "ple" "nana" "erry"

Vectorized first/last arguments

text <- "ABCDEF"
# Different start positions for each element
substring(text, c(1, 2, 3))
# [1] "ABCDEF" "BCDEF"  "CDEF"

# Different lengths via last parameter
substring(text, 1, c(2, 4, 6))
# [1] "AB"    "ABCD"  "ABCDEF"

Common Patterns

Get file extension

filename <- "report.pdf"
ext_start <- nchar(filename) - 2
substring(filename, ext_start)
# [1] "pdf"

Last n characters

text <- "example.txt"
n <- 4
substring(text, nchar(text) - n + 1)
# [1] "e.txt"

See Also

• base::substr
• stringr::strsplit
• stringr::gsub
• stringr::nchar