Issue: User could enter anything for areaPolygon and an uninformative error would be thrown. areaPolgon should be a character string or an sf object
added: throw error with message if character string is anything other than default
added: throw error with message if shapefile is not an sf object
added areaPolygon description in strat_prep to inform user they can use character string or sf
removed inherited tag (get_area) from strat_prep since definition of areaPolgon is different for each function
(get_area requires a sf object, strat_prep requires either a string or sf object)
Issue: User could enter anything for
areaPolygonand an uninformative error would be thrown.areaPolgonshould be a character string or an sf objectsfobjectareaPolygondescription instrat_prepto inform user they can use character string orsfinheritedtag (get_area) fromstrat_prepsince definition ofareaPolgonis different for each function (get_arearequires a sf object,strat_preprequires either a string or sf object)