前幾天看到這個(gè)terra包里的這個(gè)函數(shù)比較有趣，記錄一下

Cartogram:

百度百科：按照各區(qū)域單元屬性值的區(qū)際比例，調(diào)整每個(gè)區(qū)域單元的幾何面積，同時(shí)保持各個(gè)區(qū)域單元的空間鄰接關(guān)系。 以這種方式制作的地圖被稱之為?Cartogram（變形地圖），統(tǒng)計(jì)地圖，扭曲地圖，夸張地圖等等

維基百科：

A?cartogram?(also called a?value-area map?or an?anamorphic map, the latter common among German-speakers) is a?thematic map?of a set of features (countries, provinces, etc.), in which their geographic size is altered to be?directly proportional?to a selected?ratio-level?variable, such as travel time,?population, or?GNP. Geographic space itself is thus warped, sometimes extremely, in order to visualize the distribution of the variable. It is one of the most abstract types of?map; in fact, some forms may more properly be called?diagrams. They are primarily used to display emphasis and for analysis as?nomographs.

Cartograms leverage the fact that size is the most intuitive?visual variable?for representing a total amount.[2]?In this, it is a strategy that is similar to?proportional symbol maps, which scale point features, and many?flow maps, which scale the weight of linear features. However, these two techniques only scale the?map symbol, not space itself; a map that stretches the length of linear features is considered a linear cartogram (although additional flow map techniques may be added). Once constructed, cartograms are often used as a base for other thematic mapping techniques to visualize additional variables, such as?choropleth mapping.

機(jī)翻：變形圖(也稱為價(jià)值區(qū)域地圖或變形地圖，后者在講德語(yǔ)的人中很常見(jiàn))是一系列特征(國(guó)家、省等)的專題地圖，其中地理大小被改變成與選定的比率級(jí)變量成正比，如旅行時(shí)間、人口或 GNP。地理空間本身是扭曲的，有時(shí)是極端的，為了可視化的分布的變量。它是最抽象的地圖類型之一; 事實(shí)上，有些形式可能更適當(dāng)?shù)胤Q為圖。它們主要用來(lái)表示重點(diǎn)和作為諾模圖進(jìn)行分析。

變形圖的杠桿作用的事實(shí)是，大小是最直觀的視覺(jué)變量代表一個(gè)總額。在這方面，它是一種類似于比例符號(hào)映射(比例點(diǎn)特征)和許多流程映射(比例線特征的權(quán)重)的策略。然而，這兩種技術(shù)只能縮放地圖符號(hào)，而不能縮放空間本身; 一張延伸線性特征長(zhǎng)度的地圖被認(rèn)為是線性地圖(盡管可能會(huì)添加其他流動(dòng)地圖技術(shù))。變形圖一旦建立，通常用作其他專題制圖技術(shù)的基礎(chǔ)，以可視化其他變量，如脈絡(luò)圖制圖。

搜索結(jié)果有很多關(guān)于變形圖的文章和案例，但是和terra包的這個(gè)感覺(jué)不太一樣。terra包所謂的變形圖的各個(gè)part并沒(méi)有保留原有鄰接的拓?fù)潢P(guān)系，反而更像是根據(jù)原來(lái)part的value進(jìn)行了縮放。