are a vector of range edges, separated by _, continuous?

is_continuous_categories.R

## this function will print "TRUE" if the categories defined by the vector are
## continuous, e.g. c("1500_20000","20000_NA","0_1500" ) `
is_continuous_categories <- function(cat_vector){
  cat_range <- cat_vector %>%
    str_split("_") %>%
    transpose %>%
    map(unlist) %>%
    {c(invoke(setdiff, .), invoke(setdiff, rev(.)))}

  identical(cat_range, c("0", "NA"))
}