如何在GGally ggpairs中按类着色 - ggplot2 - R并将代码嵌入到函数中

Question

我在cnicollet的帮助下开发了代码 - 请参阅下面的评论 - 从GGally包中定制ggpairs - 见下文 - 并按年份分配颜色（以便年份之间的差异变得明显）：

library(ISLR)

library(data.table)
library(GGally)
library(ggplot2)
data(Auto, package = "ISLR")

Auto2 <- Auto[, c(1:3, 7:8)]

Auto2$year = ifelse(Auto2$year < 76, 0, 1)

Auto2$cylinders <- factor(Auto2$cylinders)

Auto2$origin <- factor(Auto2$origin)

Auto2$year <- factor(Auto2$year)

ggpairs(Auto2 , ggplot2::aes(colour=year),
    lower = list(continuous = wrap("points", color = "red", alpha = 0.5), 
                 combo = wrap("box", color = "orange", alpha = 0.3), 
                 discrete = wrap("facetbar", color = "yellow", alpha = 0.3) ), 
    diag = list(continuous = wrap("densityDiag",  color = "blue", alpha = 0.5) ))

现在我想将调用嵌入到一个函数中，该函数将包含表示该类的变量的数据和名称作为参数，并将该图作为对象返回而不显示它。

首先尝试：

pairplots = function(data,  class){

    library(GGally)
    library(ggplot2)

   p = ggpairs(data , ggplot2::aes(colour= class),
        lower = list(continuous = wrap("points", color = "red", alpha = 0.5), 
                     combo = wrap("box", color = "orange", alpha = 0.3), 
                     discrete = wrap("facetbar", color = "yellow", alpha = 0.3) ), 
        diag = list(continuous = wrap("densityDiag",  color = "blue", alpha = 0.5) ))


    p

}

pairplots(data = Auto2,  class = 'year')

第二次尝试：

pairplots = function(data,  class){

    library(GGally)
    library(ggplot2)


   p = ggpairs(data , ggplot2::aes(colour= data[, class]),
        lower = list(continuous = wrap("points", color = "red", alpha = 0.5), 
                     combo = wrap("box", color = "orange", alpha = 0.3), 
                     discrete = wrap("facetbar", color = "yellow", alpha = 0.3) ), 
        diag = list(continuous = wrap("densityDiag",  color = "blue", alpha = 0.5) ))


    p

}

pairplots(data = Auto2,  class = 'year')

两次尝试都会导致异常。

您的建议将不胜感激。