Is there a shorter way to extract a date from a string?

Question

I wrote code to extract the date from a given string. Given

  > \"Date: 2012-07-29, 12:59AM PDT\"

it extracts

  > \"         


        

Answer 1

As (pretty much) always, you've got multiple options here. Though none of them really frees you from getting used to some basic regular expression syntax (or its close friends).

raw_date <- "Date: 2012-07-29, 12:59AM PDT"

Alternative 1

> gsub(",", "", unlist(strsplit(raw_date, split=" "))[2])
[1] "2012-07-29"

Alternative 2

> temp <- gsub(".*: (?=\\d?)", "", raw_date, perl=TRUE)
> out <- gsub("(?<=\\d),.*", "", temp, perl=TRUE)
> out
[1] "2012-07-29"

Alternative 3

> require("stringr")
> str_extract(raw_date, "\\d{4}-\\d{2}-\\d{2}")
[1] "2012-07-29"