pattern {operators}

Pattern matching operators

Description

Set of convenience functions to handle strings and pattern matching. These are basically companion binary operators for the classic R function grep and regexpr.

Usage

  x %~% rx
  x %!~% rx
  
  x %~*% rx
  x %!~*% rx

  x %~+% rx
  x %!~+% rx
  

Arguments

x

text to manipulate

rx

regular expression

Value

%~% : gives a logical vector indicating which elements of x match the regular expression rx. %!~% is the negation of %~%

%~*% : gives a single logical indicating if all the elements of x are matching the regular expression rx. %!~*% is the negation of %~*%.

%~+% : gives a single logical indicating if any element of x matches the regular expression rx. %!~+% is the negation of %~+%.

Note

The matching is done using a modified version of the regexpr function. The modification is performed by applying the operators.regexpr option to the regexpr function via the %but% operator.

The default version of regexpr enables the perl and extended options. See %but% for details.

Author(s)

Romain Francois <[e-mail]>

See Also

grep, gsub, %~|% for regular expression filters

Examples

                        
  txt <- c("arm","foot","lefroo", "bafoobar")
  txt %~% "foo"
  txt %!~% "foo"
  txt %~*% "foo"
  txt %~+% "foo"
  txt %!~*% "foo"
  txt %!~+% "foo"
  
  txt %~%   "[a-z]"
  txt %!~%  "[a-z]"
  txt %~*%  "[a-z]"
  txt %~+%  "[a-z]"
  txt %!~*% "[a-z]"
  txt %!~+% "[a-z]"
  
  
  cols <- colors()
  cols[ cols %~% "^blue" ]
  # see also %~|%
  
  
  ## needs perl regular expression for the \\d, see %but%
  with( options( operators.regexpr = "p" ), {
  	cols[ cols %!~% "\\d$" ]
  } )