为什么两个ggplot对象通过all.equal()测试,但是不能通过same()测试？

Question

我想测试ggplot生成的两个图是否相同.一种选择是all.equal在情节对象上使用,但我宁愿进行更难的测试以确保它们是相同的,这似乎是identical()我提供的东西.

但是,当我测试两个使用相同 data和相同 创建的绘图对象时aes,我发现它们all.equal()识别它们是相同的,而对象没有通过identical测试.我不确定为什么,我想要了解更多.

基本示例:

graph <- ggplot2::ggplot(data = iris, aes(x = Species, y = Sepal.Length))
graph2 <- ggplot2::ggplot(data = iris, aes(x = Species, y = Sepal.Length))

all.equal(graph, graph2)
# [1] TRUE

identical(graph, graph2)
# [1] FALSE

Answer 1

的graph和graph2对象包含环境和环境产生它每次是不同的,即使它保持相同的值.如果R列表具有相同的内容但是列表环境具有对象标识,则R列表是相同的.尝试:

dput(graph)

给予其包括由表示环境以下<environment>的dput输出:(输出后续)

...snip...
), class = "factor")), .Names = c("Sepal.Length", "Sepal.Width", 
"Petal.Length", "Petal.Width", "Species"), row.names = c(NA, 
-150L), class = "data.frame"), layers = list(), scales = <environment>, 
    mapping = structure(list(x = Species, y = Sepal.Length), .Names = c("x", 
    "y"), class = "uneval"), theme = list(), coordinates = <environment>, 
    facet = <environment>, plot_env = <environment>, labels = structure(list(
        x = "Species", y = "Sepal.Length"), .Names = c("x", "y"
    ))), .Names = c("data", "layers", "scales", "mapping", "theme", 
"coordinates", "facet", "plot_env", "labels"), class = c("gg", 
"ggplot"))

例如,考虑:

g <- new.env()
g$a <- 1

g2 <- new.env()
g2$a <- 1

identical(as.list(g), as.list(g2))
## [1] TRUE

all.equal(g, g2)
## [1] TRUE

identical(g, g2)
## [1] FALSE