Does R have function startswith or endswith like python? [closed]

As added to base in 3.3.0, startsWith (and endsWith) are exactly this.

> startsWith("what", "wha")
[1] TRUE
> startsWith("what", "ha")
[1] FALSE

https://stat.ethz.ch/R-manual/R-devel/library/base/html/startsWith.html

Not inbuilt like that.

Options include grepl and substr.

x <- 'ABCDE'
grepl('^AB', x) # starts with AB?
grepl('DE$', x) # ends with DE?
substr(x, 1, 2) == 'AB'
substr('ABCDE', nchar(x)-1, nchar(x)) == 'DE'

The dplyr package's select statement supports starts_with and ends_with. For example, this selects the columns of the iris data frame that start with Petal

library(dplyr)
select(iris, starts_with("Petal"))

select supports other subcommands too. Try ?select .

The simplest way I can think of is to use the %like% operator:

library(data.table)

"foo" %like% "^f" 

evaluates as TRUE - Starting with f

"foo" %like% "o$" 

evaluates as TRUE - Ending with o

"bar" %like% "a"

evaluates as TRUE - Containing a

Borrowing some code from the dplyr package [see this] you could do something like this:

starts_with <- function(vars, match, ignore.case = TRUE) {
  if (ignore.case) match <- tolower(match)
  n <- nchar(match)

  if (ignore.case) vars <- tolower(vars)
  substr(vars, 1, n) == match
}

ends_with <- function(vars, match, ignore.case = TRUE) {
  if (ignore.case) match <- tolower(match)
  n <- nchar(match)

  if (ignore.case) vars <- tolower(vars)
  length <- nchar(vars)

  substr(vars, pmax(1, length - n + 1), length) == match
}