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\name{sedit}
\alias{sedit}
\alias{substring.location}
\alias{substring2}
\alias{substring2<-}
\alias{replace.substring.wild}
\alias{numeric.string}
\alias{all.digits}
\title{
Character String Editing and Miscellaneous Character Handling Functions
}
\description{
This suite of functions was written to implement many of the features
of the UNIX \code{sed} program entirely within S (function \code{sedit}).
The \code{substring.location} function returns the first and last position
numbers that a sub-string occupies in a larger string. The \code{substring2<-}
function does the opposite of the builtin function \code{substring}.
It is named \code{substring2} because for S-Plus there is a built-in
function \code{substring}, but it does not handle multiple replacements in
a single string.
\code{replace.substring.wild} edits character strings in the fashion of
"change xxxxANYTHINGyyyy to aaaaANYTHINGbbbb", if the "ANYTHING"
passes an optional user-specified \code{test} function. Here, the
"yyyy" string is searched for from right to left to handle
balancing parentheses, etc. \code{numeric.string}
and \code{all.digits} are two examples of \code{test} functions, to check,
respectively if each of a vector of strings is a legal numeric or if it contains only
the digits 0-9. For the case where \code{old="*$" or "^*"}, or for
\code{replace.substring.wild} with the same values of \code{old} or with
\code{front=TRUE} or \code{back=TRUE}, \code{sedit} (if \code{wild.literal=FALSE}) and
\code{replace.substring.wild} will edit the largest substring
satisfying \code{test}.
\code{substring2} is just a copy of \code{substring} so that
\code{substring2<-} will work.
}
\usage{
sedit(text, from, to, test, wild.literal=FALSE)
substring.location(text, string, restrict)
# substring(text, first, last) <- setto # S-Plus only
replace.substring.wild(text, old, new, test, front=FALSE, back=FALSE)
numeric.string(string)
all.digits(string)
substring2(text, first, last)
substring2(text, first, last) <- value
}
\arguments{
\item{text}{
a vector of character strings for \code{sedit, substring2, substring2<-}
or a single character string for \code{substring.location,
replace.substring.wild}.
}
\item{from}{
a vector of character strings to translate from, for \code{sedit}.
A single asterisk wild card, meaning allow any sequence of characters
(subject to the \code{test} function, if any) in place of the \code{"*"}.
An element of \code{from} may begin with \code{"^"} to force the match to
begin at the beginning of \code{text}, and an element of \code{from} can end with
\code{"$"} to force the match to end at the end of \code{text}.
}
\item{to}{
a vector of character strings to translate to, for \code{sedit}.
If a corresponding element in \code{from} had an \code{"*"}, the element
in \code{to} may also have an \code{"*"}. Only single asterisks are allowed.
If \code{to} is not the same length as \code{from}, the \code{rep} function
is used to make it the same length.
}
\item{string}{
a single character string, for \code{substring.location}, \code{numeric.string},
\code{all.digits}
}
\item{first}{
a vector of integers specifying the first position to replace for
\code{substring2<-}. \code{first} may also be a vector of character strings
that are passed to \code{sedit} to use as patterns for replacing
substrings with \code{setto}. See one of the last examples below.
}
\item{last}{
a vector of integers specifying the ending positions of the character
substrings to be replaced. The default is to go to the end of
the string. When \code{first} is character, \code{last} must be
omitted.
}
\item{setto}{
a character string or vector of character strings used as replacements,
in \code{substring2<-}
}
\item{old}{
a character string to translate from for \code{replace.substring.wild}.
May be \code{"*$"} or \code{"^*"} or any string containing a single \code{"*"} but
not beginning with \code{"^"} or ending with \code{"$"}.
}
\item{new}{
a character string to translate to for \code{replace.substring.wild}
}
\item{test}{
a function of a vector of character strings returning a logical vector
whose elements are \code{TRUE} or \code{FALSE} according
to whether that string element qualifies as the wild card string for
\code{sedit, replace.substring.wild}
}
\item{wild.literal}{
set to \code{TRUE} to not treat asterisks as wild cards and to not look for
\code{"^"} or \code{"$"} in \code{old}
}
\item{restrict}{
a vector of two integers for \code{substring.location} which specifies a
range to which the search for matches should be restricted
}
\item{front}{
specifying \code{front = TRUE} and \code{old = "*"} is the same as
specifying \code{old = "^*"}
}
\item{back}{
specifying \code{back = TRUE} and \code{old = "*"} is the same as
specifying \code{old = "*$"}
}
\item{value}{a character vector}
}
\value{
\code{sedit} returns a vector of character strings the same length as \code{text}.
\code{substring.location} returns a list with components named \code{first}
and \code{last}, each specifying a vector of character positions corresponding
to matches. \code{replace.substring.wild} returns a single character string.
\code{numeric.string} and \code{all.digits} return a single logical value.
}
\section{Side Effects}{
\code{substring2<-} modifies its first argument
}
\author{
Frank Harrell
\cr
Department of Biostatistics
\cr
Vanderbilt University School of Medicine
\cr
\email{f.harrell@vanderbilt.edu}
}
\seealso{
\code{\link{grep}}, \code{\link{substring}}
}
\examples{
x <- 'this string'
substring2(x, 3, 4) <- 'IS'
x
substring2(x, 7) <- ''
x
substring.location('abcdefgabc', 'ab')
substring.location('abcdefgabc', 'ab', restrict=c(3,999))
replace.substring.wild('this is a cat','this*cat','that*dog')
replace.substring.wild('there is a cat','is a*', 'is not a*')
replace.substring.wild('this is a cat','is a*', 'Z')
qualify <- function(x) x==' 1.5 ' | x==' 2.5 '
replace.substring.wild('He won 1.5 million $','won*million',
'lost*million', test=qualify)
replace.substring.wild('He won 1 million $','won*million',
'lost*million', test=qualify)
replace.substring.wild('He won 1.2 million $','won*million',
'lost*million', test=numeric.string)
x <- c('a = b','c < d','hello')
sedit(x, c('=','he*o'),c('==','he*'))
sedit('x23', '*$', '[*]', test=numeric.string)
sedit('23xx', '^*', 'Y_{*} ', test=all.digits)
replace.substring.wild("abcdefabcdef", "d*f", "xy")
x <- "abcd"
substring2(x, "bc") <- "BCX"
x
substring2(x, "B*d") <- "B*D"
x
}
\keyword{manip}
\keyword{character}
% Converted by Sd2Rd version 1.21.
|
