Beta
Table of Contents
The outline of your notebook will show up here. You can include headings in any text cell by starting a line with #
, ##
, ###
, etc., depending on the desired title hierarchy.
if(!require('stringr')) {
install.packages('stringr')
library('stringr')
}
hw <- "Hadley Wickham"
# Negative indices
str_sub(hw, -1)
str_sub(hw, -7)
str_sub(hw, end = -7)
# 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