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 = 1000000)
substr(x, start, stop) <- value
substring(text, first, last = 1000000) <- value

Arguments

x, text a character vector
start, first integer. The first element to be replaced.
stop, last integer. The last element to be 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 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.

Value

For substr, a character vector of the same length as x.
For substring, a character vector of length the longest of the arguments.

Note

The S4 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 nchar(type="c").

References

Becker, R. A., Chambers, J. M. and Wilks, A. R. (1988) The New S Language. Wadsworth & Brooks/Cole. (substring.)

See Also

strsplit, paste, nchar.

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)

substring(x, 2) <- c("..", "+++")
x

[Package base version 2.1.0 Index]