如何根据变量将点大小添加到Gadfly（Julia）散点图

Question

我正在尝试重现 this 使用gadfly使用gadfly。

到目前为止，我拥有的代码是：

using CSV, DataFrames, Gadfly

download("https://raw.githubusercontent.com/mwaskom/seaborn-data/master/mpg.csv", "mpg.csv");
mpg = DataFrame(CSV.File("mpg.csv"));

p = plot(
     mpg, 
     x = :horsepower, 
     y = :mpg, 
     color = :origin, 
     #size = :weight, 
     alpha = [0.5], 
     Geom.point,
     Theme(background_color = "white"),
     )

如何添加圆的大小以匹配汽车权重并将其添加为第二个传说？

Answer 1

请参阅话语：

p = plot(
    mpg,
    x = :horsepower,
    y = :mpg,
    color = :origin,
    size = :weight,
    alpha = [0.5],
    Geom.point,
    Theme(background_color = "white"),
    Scale.size_area(maxvalue=maximum(mpg.weight)),
)