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\alias{startsWith}
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\alias{startsWith}
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\description{
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\description{
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  Determines if entries of \code{x} start or end with string (entries of)
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  Determines if entries of \code{x} start or end with string (entries of)
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  \code{prefix} or \code{suffix} respectively, where strings are
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  \code{prefix} or \code{suffix} respectively, where strings are
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  recycled to common lengths.
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  recycled to common lengths.
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  \code{startsWith()} is equivalent to but much faster than
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  \preformatted{substring(x, 1, nchar(prefix)) == prefix}
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  or also \preformatted{grepl("^<prefix>", x)} where \code{prefix} is
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  not to contain special regular expression characters.
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}
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}
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\usage{
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\usage{
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startsWith(x, prefix)
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startsWith(x, prefix)
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  endsWith(x, suffix)
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  endsWith(x, suffix)
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}
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}
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  \item{x}{vector of \code{\link{character}} string whose \dQuote{starts}
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  \item{x}{vector of \code{\link{character}} string whose \dQuote{starts}
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    are considered.}
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    are considered.}
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  \item{prefix, suffix}{\code{\link{character}} vector (often of length one).}
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  \item{prefix, suffix}{\code{\link{character}} vector (often of length one).}
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}
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}
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\details{
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\details{
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  \code{startsWith()} is equivalent to but much faster than
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\preformatted{  substring(x, 1, nchar(prefix)) == prefix  }
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  or also
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\preformatted{  grepl("^<prefix>", x)  }
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  where \code{prefix} is not to contain special regular expression
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  characters (and for \code{grepl}, \code{x} does not contain missing
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  values, see below).
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  The code has an optimized branch for the most common usage in which
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  The code has an optimized branch for the most common usage in which
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  \code{prefix} or \code{suffix} is of length one, and is further
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  \code{prefix} or \code{suffix} is of length one, and is further
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  optimized in a UTF-8 or 8-byte locale if that is an ASCII string.
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  optimized in a UTF-8 or 8-byte locale if that is an ASCII string.
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}
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}
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\value{
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\value{
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      startsWith(x1, "bla"),
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      startsWith(x1, "bla"),
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        endsWith(x1, "n"),
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        endsWith(x1, "n"),
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        endsWith(x1, "an"))
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        endsWith(x1, "an"))
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rownames(x2) <- x1; colnames(x2) <- c("b", "b1", "bla", "n", "an")
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rownames(x2) <- x1; colnames(x2) <- c("b", "b1", "bla", "n", "an")
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x2
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x2
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## Non-equivalence in case of missing values in 'x', see Details:
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x <- c("all", "but", NA_character_)
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cbind(startsWith(x, "a"),
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      substring(x, 1L, 1L) == "a",
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      grepl("^a", x))
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}
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}
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\keyword{character}
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\keyword{character}
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\keyword{utilities}
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\keyword{utilities}