keep_re {mclm}

Subset an object based on regular expressions

Description

These methods can be used to subset objects based on a regular expression.

Usage

keep_re(x, pattern, perl = TRUE, invert = FALSE, ...)

drop_re(x, pattern, perl = TRUE, ...)

## S3 method for class 'fnames'
drop_re(x, pattern, perl = TRUE, ...)

## S3 method for class 'fnames'
keep_re(x, pattern, perl = TRUE, invert = FALSE, ...)

## S3 method for class 'freqlist'
drop_re(x, pattern, perl = TRUE, ...)

## S3 method for class 'freqlist'
keep_re(x, pattern, perl = TRUE, invert = FALSE, ...)

## S3 method for class 'tokens'
drop_re(x, pattern, perl = TRUE, ...)

## S3 method for class 'tokens'
keep_re(x, pattern, perl = TRUE, invert = FALSE, ...)

## S3 method for class 'types'
drop_re(x, pattern, perl = TRUE, ...)

## S3 method for class 'types'
keep_re(x, pattern, perl = TRUE, invert = FALSE, ...)

Arguments

x

An object of any of the classes for which the method is implemented.

pattern

Either an object of the class re or a character vector of length one containing a regular expression.

perl

Logical. Whether pattern is treated as a PCRE flavor regular expression. The perl argument is only used if pattern is a regular character vector. If pattern is an object of the class re, then the perl argument is ignored, and the relevant information in the re object pattern, viz. the value of pattern$perl, is used instead.

invert

Logical. Whether the matches should be selected rather than the non-matches.

...

Additional arguments.

Details

The methods keep_pos() and drop_pos() are part of a family of methods of the mclm package used to subset different objects. The methods starting with keep_ extract the items in x based on the criterion specified by the second argument. In contrast, the methods starting with drop_ exclude the items that match the criterion in the same argument.

Calling a drop_ method is equivalent to calling its keep_ counterpart when the invert argument is TRUE.

Value

Object of the same class as x with the selected elements only.

See Also

Other subsetters: brackets, keep_bool(), keep_pos(), keep_types()

Examples

# For a 'freqlist' object --------------------
(flist <- freqlist("The man and the mouse.", as_text = TRUE))

keep_re(flist, "[ao]")
drop_re(flist, "[ao]")
keep_re(flist, "[ao]", invert = TRUE) # same as drop_re()

# For a 'types' object -----------------------
(tps <- as_types(letters[1:10]))

keep_re(tps, "[acegi]")
drop_re(tps, "[acegi]")

# For a 'tokens' object ----------------------
(tks <- as_tokens(letters[1:10]))

keep_re(tks, "[acegi]")
drop_re(tks, "[acegi]")