Compute the longest common prefix or suffix of a string

Description

These functions find the longest common prefix or suffix among the strings in a character vector.

Usage

lcPrefix(x, ignore.case=FALSE)
lcPrefixC(x, ignore.case=FALSE)
lcSuffix(x, ignore.case=FALSE)

Arguments

Details

Computing the longest common suffix is helpful for truncating names of objects, like microarrays, that often have a common suffix, such as .CEL.

There are some potential problems with the approach used if multibyte character encodings are being used.

lcPrefixC is a faster implementation in C. It only handles ascii characters.

Value

The common prefix or suffix.

Author(s)

R. Gentleman

See Also

nchar, nchar

Examples

s1 <- c("ABC.CEL", "DEF.CEL")
lcSuffix(s1)

s2 <- c("ABC.123", "ABC.456")
lcPrefix(s2)


CHK <- stopifnot

CHK(".CEL" == lcSuffix(s1))
CHK("bc" == lcSuffix(c("abc", "333abc", "bc")))
CHK("c" == lcSuffix(c("c", "abc", "xxxc")))
CHK("" == lcSuffix(c("c", "abc", "xxx")))

CHK("ABC." == lcPrefix(s2))
CHK("ab" == lcPrefix(c("abcd", "abcd123", "ab", "abc", "abc333333")))
CHK("a" == lcPrefix(c("abcd", "abcd123", "ax")))
CHK("a" == lcPrefix(c("a", "abcd123", "ax")))
CHK("" == lcPrefix(c("a", "abc", "xxx")))

CHK("ab" == lcPrefixC(c("abcd", "abcd123", "ab", "abc", "abc333333")))
CHK("a" == lcPrefixC(c("abcd", "abcd123", "ax")))
CHK("a" == lcPrefixC(c("a", "abcd123", "ax")))
CHK("" == lcPrefixC(c("a", "abc", "xxx")))