| substr {base} | R Documentation |
Substrings of a Character Vector
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 element to be extracted or replaced. |
stop, last |
integer. The last element to be extracted or replaced. |
value |
a character vector, recycled if necessary. |
Details
substring is compatible with S, with first and
last 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.
For the extraction functions, x or text will be
converted to a character vector by as.character 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 is an NA element, the corresponding element of
the answer is NA.
Elements of the result will be have the encoding declared as that of
the current locale (see Encoding) 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), 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).
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 from
x if it is the longest of the arguments).
For the replacement functions, a character vector of the same length as
x or text, with attributes such as
names preserved.
Elements of x or text with a declared encoding (see
Encoding) 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 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), but at least make sure you use the default
nchar(type = "chars").
References
Becker, R. A., Chambers, J. M. and Wilks, A. R. (1988)
The New S Language.
Wadsworth & Brooks/Cole. (substring.)
See Also
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)))