Substrings of a Character Vector (original) (raw)
| substr {base} | R Documentation |
|---|
Description
Extract or replace substrings in a character vector.
Usage
substr(x, start, stop)
substring(text, first, last = 1000000L)
substr(x, start, stop) <- value
substring(text, first, last = 1000000L) <- value
Arguments
| x, text | a character vector. |
|---|---|
| start, first | integer. The first character to be extracted or replaced. |
| stop, last | integer. The last character to be extracted or replaced. |
| value | a character vector, recycled if necessary. |
Details
substring is compatible with S, with first andlast instead of start and stop. For vector arguments, it expands the arguments cyclically to the length of the longest provided none are of zero length.
When extracting, if start is larger than the string length then"" is returned. If stop is larger than the string length then the portion until the end of the string is returned.
For the extraction functions, x or text will be converted to a character vector by [as.character](../../base/help/as.character.html) if it is not already one.
For the replacement functions, if start is larger than the string length then no replacement is done. If the portion to be replaced is longer than the replacement string, then only the portion the length of the string is replaced.
If any argument has an NA element, the corresponding element of the answer is NA.
Elements of the result will have the encoding declared as that of the current locale (see [Encoding](../../base/help/Encoding.html)) if the corresponding input had a declared Latin-1 or UTF-8 encoding and the current locale is either Latin-1 or UTF-8.
If an input element has declared "bytes" encoding (see[Encoding](../../base/help/Encoding.html)), the subsetting is done in units of bytes not characters.
Value
For substr, a character vector of the same length and with the same attributes as x (after possible coercion). start andstop are recycled as necessary.
For substring, a character vector of length the longest of the arguments. This will have names taken from x (if it has any after coercion, repeated as needed), and other attributes copied fromx if it is the longest of the arguments).
For the replacement functions, a character vector of the same length asx or text, with [attributes](../../base/help/attributes.html) such as[names](../../base/help/names.html) preserved.
Elements of x or text with a declared encoding (see[Encoding](../../base/help/Encoding.html)) will be returned with the same encoding.
Note
The S version of substring<- ignores last; this version does not.
These functions are often used with [nchar](../../base/help/nchar.html) to truncate a display. That does not really work (you want to limit the width, not the number of characters, so it would be better to use[strtrim](../../base/help/strtrim.html)), but at least make sure you use the defaultnchar(type = "chars").
References
Becker, R. A., Chambers, J. M. and Wilks, A. R. (1988)The New S Language. Wadsworth & Brooks/Cole. (substring.)
See Also
[startsWith](../../base/help/startsWith.html) and [endsWith](../../base/help/endsWith.html);[strsplit](../../base/help/strsplit.html), [paste](../../base/help/paste.html), [nchar](../../base/help/nchar.html).
Examples
substr("abcdef", 2, 4)
substring("abcdef", 1:6, 1:6)
## strsplit() is more efficient ...
substr(rep("abcdef", 4), 1:4, 4:5)
x <- c("asfef", "qwerty", "yuiop[", "b", "stuff.blah.yech")
substr(x, 2, 5)
substring(x, 2, 4:6)
X <- x
names(X) <- LETTERS[seq_along(x)]
comment(X) <- noquote("is a named vector")
str(aX <- attributes(X))
substring(x, 2) <- c("..", "+++")
substring(X, 2) <- c("..", "+++")
X
stopifnot(x == X, identical(aX, attributes(X)), nzchar(comment(X)))
[Package _base_ version 4.6.0 Index]