1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
|
% Generated by roxygen2: do not edit by hand
% Please edit documentation in R/sub.R
\name{stri_sub}
\alias{stri_sub}
\alias{stri_sub<-}
\alias{stri_sub_replace}
\title{Extract a Substring From or Replace a Substring In a Character Vector}
\usage{
stri_sub(
str,
from = 1L,
to = -1L,
length,
use_matrix = TRUE,
ignore_negative_length = FALSE
)
stri_sub(str, from = 1L, to = -1L, length, omit_na = FALSE, use_matrix = TRUE) <- value
stri_sub_replace(..., replacement, value = replacement)
}
\arguments{
\item{str}{character vector}
\item{from}{integer vector giving the start indexes; alternatively,
if \code{use_matrix=TRUE},
a two-column matrix of type \code{cbind(from, to)}
(unnamed columns or the 2nd column named other than \code{length})
or \code{cbind(from, length=length)} (2nd column named \code{length})}
\item{to}{integer vector giving the end indexes; mutually exclusive with
\code{length} and \code{from} being a matrix}
\item{length}{integer vector giving the substring lengths;
mutually exclusive with \code{to} and \code{from} being a matrix}
\item{use_matrix}{single logical value; see \code{from}}
\item{ignore_negative_length}{single logical value; whether
negative lengths should be ignored or result in missing values}
\item{omit_na}{single logical value; indicates whether missing values
in any of the indexes or in \code{value} leave the corresponding input string
unchanged [replacement function only]}
\item{value}{a character vector defining the replacement strings
[replacement function only]}
\item{...}{arguments to be passed to \code{stri_sub<-}}
\item{replacement}{alias of \code{value} [wherever applicable]}
}
\value{
\code{stri_sub} and \code{stri_sub_replace} return a character vector.
\code{stri_sub<-} changes the \code{str} object 'in-place'.
}
\description{
\code{stri_sub} extracts particular substrings at code point-based
index ranges provided. Its replacement version allows to substitute
(in-place) parts of
a string with given replacement strings. \code{stri_sub_replace}
is its forward pipe operator-friendly variant that returns
a copy of the input vector.
For extracting/replacing multiple substrings from/within each string, see
\code{\link{stri_sub_all}}.
}
\details{
Vectorized over \code{str}, [\code{value}], \code{from} and
(\code{to} or \code{length}). Parameters
\code{to} and \code{length} are mutually exclusive.
Indexes are 1-based, i.e., the start of a string is at index 1.
For negative indexes in \code{from} or \code{to},
counting starts at the end of the string.
For instance, index -1 denotes the last code point in the string.
Non-positive \code{length} gives an empty string.
Argument \code{from} gives the start of a substring to extract.
Argument \code{to} defines the last index of a substring, inclusive.
Alternatively, its \code{length} may be provided.
If \code{from} is a two-column matrix, then these two columns are
used as \code{from} and \code{to}, respectively,
unless the second column is named \code{length}.
In such a case anything passed
explicitly as \code{to} or \code{length} is ignored.
Such types of index matrices are generated by \code{\link{stri_locate_first}}
and \code{\link{stri_locate_last}}. If extraction based on
\code{\link{stri_locate_all}} is needed, see
\code{\link{stri_sub_all}}.
In \code{stri_sub}, out-of-bound indexes are silently
corrected. If \code{from} > \code{to}, then an empty string is returned.
By default, negative \code{length} results in the corresponding output being
\code{NA}, see \code{ignore_negative_length}, though.
In \code{stri_sub<-}, some configurations of indexes may work as
substring 'injection' at the front, back, or in middle.
Negative \code{length} does not alter the corresponding input string.
If both \code{to} and \code{length} are provided,
\code{length} has priority over \code{to}.
Note that for some Unicode strings, the extracted substrings might not
be well-formed, especially if input strings are not normalized
(see \code{\link{stri_trans_nfc}}),
include byte order marks, Bidirectional text marks, and so on.
Handle with care.
}
\examples{
s <- c("spam, spam, bacon, and spam", "eggs and spam")
stri_sub(s, from=-4)
stri_sub(s, from=1, length=c(10, 4))
(stri_sub(s, 1, 4) <- 'stringi')
x <- c('12 3456 789', 'abc', '', NA, '667')
stri_sub(x, stri_locate_first_regex(x, '[0-9]+')) # see stri_extract_first
stri_sub(x, stri_locate_last_regex(x, '[0-9]+')) # see stri_extract_last
stri_sub_replace(x, stri_locate_first_regex(x, '[0-9]+'),
omit_na=TRUE, replacement='***') # see stri_replace_first
stri_sub_replace(x, stri_locate_last_regex(x, '[0-9]+'),
omit_na=TRUE, replacement='***') # see stri_replace_last
\dontrun{x |> stri_sub_replace(1, 5, replacement='new_substring')}
}
\seealso{
The official online manual of \pkg{stringi} at \url{https://stringi.gagolewski.com/}
Gagolewski M., \pkg{stringi}: Fast and portable character string processing in R, \emph{Journal of Statistical Software} 103(2), 2022, 1-59, \doi{10.18637/jss.v103.i02}
Other indexing:
\code{\link{stri_locate_all_boundaries}()},
\code{\link{stri_locate_all}()},
\code{\link{stri_sub_all}()}
}
\concept{indexing}
\author{
\href{https://www.gagolewski.com/}{Marek Gagolewski} and other contributors
}
|
