R dplyr: Filter data by multiple Regex expressions defined by vector

Question

I have a dataframe, from which I want to select important columns, and then filter the rows to contain specific ending.

Regex expression make it simple to define my

Answer 1

You may use

df %>% 
  select(x, y) %> filter(grepl(paste0("(?:", paste(ids, collapse="|"), ")$"), y))

The paste0("(?:", paste(ids, collapse="|"), ")$") part will build an alternation pattern that will only match at the end of the string due to $ anchor at the end.

NOTE: If the values can have special regex metacharacters you need to escape the values in the character vector first:

regex.escape <- function(string) {
  gsub("([][{}()+*^$|\\\\?.])", "\\\\\\1", string)
}
df %>% 
      select(x, y) %> filter(grepl(paste0("(?:", paste(regex.escape(ids), collapse="|"), ")$"), y))
                                                       ^^^^^^^^^^^^^^^^^

For example, paste0("(?:", paste(c("7", "8", "ids"), collapse="|"), ")$") will output (?:7|8|ids)$:

• (?: - start of a non-capturing group that will act as a container for the alternatives, so that the $ anchor applied to all of them and not to just the last one, matching any of
• • 7 - a 7 char
• | - or
• 8 - an 8 char
• | - or
• ids - an ids substring
• ) - end of the group
• $ - end of the string.