How to determine if a string "ends with" another string in R?

Question

I want to filter out the rows of a table which contain '*' in the string value of the column. Checking just that column.

 string_name = c("aaaaa", "bbbbb", "ccccc", "dddd*", "eee*eee")

 zz <- sapply(tx$variant_full_name, function(x) {substrRight(x, -1) =="*"})
 Error in FUN(c("Agno I30N", "VP2 E17Q", "VP2 I204*", "VP3 I85F", "VP1 K73R",  : 
   could not find function "substrRight"

The 4th value of zz should be TRUE by this.

in python there is endswith function for strings [ string_s.endswith('*') ] Is there something similar to that in R ?

Also, is it problem because of '*' as a character as it means any character ? grepl also not working.

> grepl("*^",'dddd*')
[1] TRUE
> grepl("*^",'dddd')
[1] TRUE

Answer 1

* is a quantifier in regular expressions. It tells the regular expression engine to attempt to match the preceding token "zero or more times". To match a literal, you need to precede it with two backslashes or place inside of a character class [*]. To check if the string ends with a specific pattern, use the end of string $ anchor.

> grepl('\\*$', c('aaaaa', 'bbbbb', 'ccccc', 'dddd*', 'eee*eee'))
# [1] FALSE FALSE FALSE  TRUE FALSE

You can simply do this without implementing a regular expression in base R:

> x <- c('aaaaa', 'bbbbb', 'ccccc', 'dddd*', 'eee*eee')
> substr(x, nchar(x)-1+1, nchar(x)) == '*'
# [1] FALSE FALSE FALSE  TRUE FALSE