R function to test is vector of datetimes is regular and continuous

is_regular.R

is.regular <- function(x) {
  # returns TRUE if vector x of POSIXct datetimes is continuous and regular
  # by checking if there are more than one unique difftime between each row
  x.difftime <- difftime(x[2:length(x)], x[1:(length(x)-1)], units='secs')
  if (length(levels(factor(x.difftime))) > 1) {
    return (FALSE)
  } else {
    return (TRUE)
  }
}