substr                 package: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 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'.

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).

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

