Testing dates in R - an IsDate() function

isdate.R

# Trying to find a basic test for dates in R. was looking for a is.Date like as.Date vibe

IsDate <- function(mydate, date.format = "%d/%m/%y") {
  # Check if field is a date using as.Date that looks for unambiguous dates
  #   Assumes date format so NA returned not Character error. 
  #   Why? with no date format, R tries two defaults then gives error. 
  #   BUT With a dateformat R returns NA
  # Args
  #   Suspected date and optional date format string
  # Returns
  #   TRUE if thinbks it is a date
  tryCatch(!is.na(as.Date(mydate, date.format)),  
           error = function(err) {FALSE})  
}

mydate <- "price"

IsDate(mydate)
# FALSE
mydate <- "1/3/2015"

IsDate(mydate)
# TRUE

the code can be improved with various date formats using tryFormats param in as.Date()

library(lubridate)
IsDate <- function(mydate) {
  	tryCatch(!is.na(as.Date(mydate, "",tryFormats = c("%Y-%m-%d", "%Y/%m/%d","%d-%m-%Y","%m-%d-%Y"))),  
        error = function(err) {FALSE})  
}

Really useful function @micstr, thanks!

@dips99 nice improvements!

@dips99 This function is prone to SQL injection. The following returns TRUE:

    IsDate("2020-08-11; DROP * FROM table")

The base R function seems to work as intended:

is_date = function(x, format) {
  formatted = try(as.Date(x, format), silent = TRUE)
  return(as.character(formatted) == x)
}

If I see it right, this cannot handle e.g. NAs. I instead suggest using

is_date_new <- function(date, format) {
  formatted = try(as.Date(date, format), silent = TRUE)
  return(DIZutils::equals2(as.character(formatted), date))
}

which leads to a TRUE/FALSE result:

date <- c("2021-01-01", "2020-12-31", "foo", "2021-31-12")
format <- "%Y-%m-%d"

## The function from above:
is_date(date, format)
#> [1] TRUE TRUE   NA   NA

## This function:
is_date_new(date, format)
#> [1]  TRUE  TRUE FALSE FALSE

^{Created on 2021-05-25 by the reprex package (v2.0.0)}