str_sub {stringr} | R Documentation |
str_sub
will recycle all arguments to be the same length as the
longest argument. If any arguments are of length 0, the output will be
a zero length character vector.
str_sub(string, start = 1L, end = -1L)
str_sub(string, start = 1L, end = -1L, omit_na = FALSE) <- value
string |
input character vector. |
start, end |
Two integer vectors. Negative values count backwards from the last character. |
omit_na |
Single logical value. If |
value |
replacement string |
Substrings are inclusive - they include the characters at both start and
end positions. str_sub(string, 1, -1)
will return the complete
substring, from the first character to the last.
A character vector of substring from start
to end
(inclusive). Will be length of longest input argument.
The underlying implementation in stringi::stri_sub()
hw <- "Hadley Wickham"
str_sub(hw, 1, 6)
str_sub(hw, end = 6)
str_sub(hw, 8, 14)
str_sub(hw, 8)
str_sub(hw, c(1, 8), c(6, 14))
# Negative indices
str_sub(hw, -1)
str_sub(hw, -7)
str_sub(hw, end = -7)
# Alternatively, you can pass in a two colum matrix, as in the
# output from str_locate_all
pos <- str_locate_all(hw, "[aeio]")[[1]]
str_sub(hw, pos)
str_sub(hw, pos[, 1], pos[, 2])
# Vectorisation
str_sub(hw, seq_len(str_length(hw)))
str_sub(hw, end = seq_len(str_length(hw)))
# Replacement form
x <- "BBCDEF"
str_sub(x, 1, 1) <- "A"; x
str_sub(x, -1, -1) <- "K"; x
str_sub(x, -2, -2) <- "GHIJ"; x
str_sub(x, 2, -2) <- ""; x
# If you want to keep the original if some argument is NA,
# use omit_na = TRUE
x1 <- x2 <- x3 <- x4 <- "AAA"
str_sub(x1, 1, NA) <- "B"
str_sub(x2, 1, 2) <- NA
str_sub(x3, 1, NA, omit_na = TRUE) <- "B"
str_sub(x4, 1, 2, omit_na = TRUE) <- NA
x1; x2; x3; x4