Hmisc (version 5.3-1)

sedit: Character String Editing and Miscellaneous Character Handling Functions

Description

This suite of functions was written to implement many of the features of the UNIX sed program entirely within S (function sedit). The substring.location function returns the first and last position numbers that a sub-string occupies in a larger string. The substring2<- function does the opposite of the builtin function substring. It is named substring2 because for S-Plus there is a built-in function substring, but it does not handle multiple replacements in a single string. replace.substring.wild edits character strings in the fashion of "change xxxxANYTHINGyyyy to aaaaANYTHINGbbbb", if the "ANYTHING" passes an optional user-specified test function. Here, the "yyyy" string is searched for from right to left to handle balancing parentheses, etc. numeric.string and all.digits are two examples of 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 old="*$" or "^*", or for replace.substring.wild with the same values of old or with front=TRUE or back=TRUE, sedit (if wild.literal=FALSE) and replace.substring.wild will edit the largest substring satisfying test.

substring2 is just a copy of substring so that 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

Value

sedit returns a vector of character strings the same length as text.

substring.location returns a list with components named first

and last, each specifying a vector of character positions corresponding to matches. replace.substring.wild returns a single character string.

numeric.string and all.digits return a single logical value.

See Also

grep, 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