clean_strings: Clean and standardize character columns

In dataprep: Fast, Efficient, and Versatile Data Preprocessing and Reshaping with 'C++', 'OpenMP' & 'SIMD'

Clean and standardize character columns

Description

Applies common string cleaning operations to character or factor columns: trimming whitespace, changing case, and applying regular expression substitutions. Numeric and other non-character columns are left untouched.

Usage

clean_strings(
  data,
  cols = NULL,
  trim = FALSE,
  tolower = FALSE,
  toupper = FALSE,
  pattern = NULL,
  replacement = NULL,
  verbose = FALSE
)

Arguments

data	A data frame, matrix, or character vector.
cols	Columns to clean. If NULL (default), all character and factor columns are selected. Columns that are neither character nor factor are skipped, so the numeric and logical columns of data are never silently coerced to character.
trim	Logical; if TRUE, leading and trailing whitespace is removed with trimws.
tolower	Logical; if TRUE, converted to lowercase.
toupper	Logical; if TRUE, converted to uppercase.
pattern	Optional regular expression passed to gsub.
replacement	Replacement string for pattern. Defaults to "" (deletion) when pattern is supplied and replacement is NULL.
verbose	Logical; if TRUE, prints timing message.

Details

The operations are applied in a fixed order:

1. trim (via trimws),

2. tolower then toupper,

3. pattern replacement (via gsub).

When both tolower and toupper are TRUE, the uppercase conversion wins (it is applied last). In practice only one of the two should be set.

For factor columns, the underlying integer codes are dropped and the column becomes a character vector. If you need to keep the factor type, convert the cleaned values back with factor().

Value

A data frame (or character vector, if the input was a vector) with the selected columns cleaned.

Examples

df <- data.frame(
  id   = 1:3,
  name = c("  Alice ", "BOB", "Charlie "),
  city = c("New York", "london", "Paris"),
  stringsAsFactors = FALSE
)

# Only the character columns are touched by default
clean_strings(df, trim = TRUE, tolower = TRUE)

# Explicit column selection
clean_strings(df, cols = "name", trim = TRUE, toupper = TRUE)

# Regex replacement
clean_strings(df, cols = "city",
              pattern = "\\s+", replacement = "_")

# Vector input
clean_strings(c(" A ", " b ", "C"), trim = TRUE, tolower = TRUE)

dataprep documentation built on Oct. 1, 2026, 5:07 p.m.