. ▁ ▁The ▁CR AN ▁package ▁rec map ▁provides ▁an ▁implementation ▁of ▁ ▁a ▁rect angular ▁cart ogram ▁algorithm . ▁ ▁Cart og rams ▁can ▁also ▁be ▁constructed ▁manually , ▁either ▁by ▁hand ▁or ▁in ▁a ▁computer - ass isted ▁environment . ▁Block ▁cart og rams ▁are ▁constructed ▁by ▁arr anging ▁geomet r ically ▁regular ▁equal - s ized ▁blocks , ▁with ▁the ▁number ▁of ▁blocks ▁allocated ▁to ▁each ▁district ▁proportional ▁to ▁the ▁population ▁variable . ▁Several ▁examples ▁of ▁block ▁cart og rams ▁were ▁published ▁during ▁the ▁ 2 0 1 6 ▁U . S . ▁president ial ▁election ▁season ▁by ▁The ▁Washington ▁Post , ▁the ▁Five Th irty E ight ▁blog , ▁and ▁the ▁Wall ▁Street ▁Journal , ▁among ▁others . ▁ ▁Alg orithms ▁ ▁See ▁also ▁ ▁References ▁ ▁External ▁links ▁ ▁Cart og rams ▁about ▁Brazil ▁ ▁Further ▁reading ▁▁ ▁Campbell , ▁John . ▁Map ▁Use ▁and ▁Analysis . ▁New ▁York : ▁McG raw - H ill , ▁ 2 0 0 1 . ▁ ▁Dor ling , ▁Daniel . ▁" Area ▁cart og rams : ▁Their ▁use ▁and ▁creation ." ▁" Con cept s ▁and ▁Te chni ques ▁in ▁Modern ▁Geography ▁series ▁no . ▁ 5 9 ." ▁Nor wich : ▁University ▁of ▁East ▁Ang lia , ▁ 1 9 9 6 . ▁ ▁Gast ner , ▁Michael ▁T . ▁and ▁Mark ▁E . ▁J . ▁New man , ▁" Diff usion - based ▁method ▁for ▁producing ▁density - equal izing ▁maps ." ▁Pro ceed ings ▁of ▁the ▁National