Extract and replace substrings from a character vector.
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
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