strsplit() in R: Split Strings by a Delimiter

The strsplit() function in base R splits each element of a character vector at a delimiter (regex or fixed) and returns a LIST of character vectors, one per input element.

strsplit("a,b,c", ",")[[1]]                # c("a","b","c")
strsplit(c("a,b","c,d"), ",")              # list of vectors
strsplit("a.b.c", ".", fixed = TRUE)[[1]]  # literal period
strsplit("a.b.c", "\\.")                   # regex period
unlist(strsplit(x, ","))                   # flatten to vector
do.call(rbind, strsplit(x, ","))           # to matrix (if even)
stringr::str_split(x, ",")                 # tidyverse equivalent

What strsplit() does in one sentence

strsplit(x, split) splits each string in x at every occurrence of split (regex by default) and returns a LIST where each element is a character vector of the parts. The list has length equal to the input.

The list output is intentional: different inputs can produce different numbers of parts. To collapse to a vector, unlist(). To force into a matrix, use do.call(rbind, ...) only when all inputs split into equal counts.

Syntax

strsplit(x, split, fixed = FALSE, perl = FALSE). Returns a LIST.

Five common patterns

1. Split CSV-like single string

2. Split a vector of strings

Variable lengths are why the result is a list, not a matrix.

3. Split by regex (e.g., any whitespace)

\\s+ matches one-or-more whitespace, so multi-space gaps collapse.

4. Split a column into a matrix (equal-length only)

Works only when all inputs split into the same number of pieces.

5. Split with fixed = TRUE (literal delimiter)

Without fixed = TRUE, . is regex (any character), splitting at every position.

strsplit() vs str_split() vs separate() vs substr()

Four ways to split strings in R, each suited to different shapes.

When to use which:

• strsplit for base R delimiter splits.
• str_split_fixed when you know the max number of pieces.
• separate to split a data frame column into named columns.
• substr for known-position splits (e.g., always at index 5).

A practical strsplit workflow

Most strsplit workflows go: split, validate, transform. Common patterns:

1. Split-and-flatten: unlist(strsplit(x, sep)) to get one big vector.
2. Split-and-stack: do.call(rbind, strsplit(x, sep)) to get a matrix.
3. Split-and-extract-Nth: sapply(strsplit(x, sep), [, 2) to grab the 2nd part of each.
4. Split-and-re-aggregate: split by some boundary, then process group-wise.

For data-frame work, tidyr::separate() is usually cleaner because it produces named columns directly.

Common pitfalls

Pitfall 1: result is always a list. strsplit("a,b", ",") returns a list, not a vector. [[1]] extracts the inner vector for single-input cases.

Pitfall 2: do.call(rbind, ...) errors on unequal lengths. If inputs split into different counts, rbind fails. Use stringr::str_split_fixed() or pad results manually.

Try it yourself

Related split functions

After mastering strsplit, look at:

• stringr::str_split(): tidyverse equivalent
• stringr::str_split_fixed(): returns a matrix directly
• tidyr::separate(): split a data frame column into multiple columns
• tidyr::separate_rows(): split into multiple ROWS (long format)
• substr() / substring(): split at fixed positions
• regmatches(): split using regex matches

For data frame column splits, tidyr::separate() saves a step over strsplit + bind.

FAQ

How do I split a string in R?

strsplit(x, ",")[[1]] for a single string. For a vector, leave off [[1]] and you get a list.

Why does strsplit return a list?

Different inputs can split into different numbers of parts. A list naturally holds variable-length results. For single-input cases, [[1]] extracts the vector.

What is the difference between strsplit and stringr str_split?

Both split a string by a regex pattern. str_split puts the string argument FIRST (pipe-friendly): str_split(x, ","). strsplit puts pattern second: strsplit(x, ","). Same result; different argument order.

How do I split into a fixed number of pieces?

stringr::str_split_fixed(x, ",", n = 3) returns a 3-column matrix. Or strsplit then head(parts, 3) per element.

How do I split a string into individual characters?

strsplit(x, "")[[1]]. Empty delimiter splits at every position. Or use unlist(strsplit("hello", "")) for a vector.