Split a Character Vector into a Dummy Matrix

Splits a character vector of delimited tokens into a binary dummy data.frame where each unique token becomes a column.

Usage

strSplitToDummy(x, split = ",", trim = TRUE, na.action = na.pass, ...)

Arguments

x

a character vector with delimited tokens.

split

a character string to use as delimiter. Default is ",".

trim

logical. If TRUE (default), whitespace is trimmed from each token after splitting.

na.action

a function to handle NA values. Accepted values are na.pass() (default), na.omit(), na.exclude(), and na.fail().

na.pass

NAs are kept as all-zero rows (default).

na.omit

rows with NAs are silently removed.

na.exclude

like na.omit but the indices of removed rows are stored in a "na.action" attribute.

na.fail

an error is raised if any NA is present.

...

additional arguments passed to strsplit().

Value

a data.frame with one row per element of x and one column per unique token. Values are 0L or 1L. Column names are the token values as-is and may not be syntactically valid R identifiers. The attribute "tokens" contains the sorted vector of unique tokens.

See also

strsplit(), na.omit()

Other string.transform: char-ascii-conversion, mGsub(), strSplitToCol()

Examples

dat <- data.frame(id = 1:5,
                  txt = c("A,C,D", "A", "B,C", "D", "D,E"))

# default: NA passed through as zero row
strSplitToDummy(dat$txt)
#>   A B C D E
#> 1 1 0 1 1 0
#> 2 1 0 0 0 0
#> 3 0 1 1 0 0
#> 4 0 0 0 1 0
#> 5 0 0 0 1 1

# with an NA in the input
x_na <- c("A,B", "B,C", NA, "A")

# na.pass: NA becomes an all-zero row (default)
strSplitToDummy(x_na, na.action = na.pass)
#>   A B C
#> 1 1 1 0
#> 2 0 1 1
#> 3 0 0 0
#> 4 1 0 0

# na.omit: NA rows are silently dropped
strSplitToDummy(x_na, na.action = na.omit)
#>   A B C
#> 1 1 1 0
#> 2 0 1 1
#> 3 1 0 0

# na.exclude: like na.omit but NA indices stored in attribute
res <- strSplitToDummy(x_na, na.action = na.exclude)
attr(res, "na.action")
#> [1] 3
#> attr(,"class")
#> [1] "exclude"

# na.fail: error if any NA present
tryCatch(
  strSplitToDummy(x_na, na.action = na.fail),
  error = function(e) conditionMessage(e)
)
#> [1] "missing values in 'x'"