有没有一种方法可以“遍历列表”？ [英] Is there a way to `pipe through a list'?

问题描述

我从未真正充分利用过的 ggplot2 包中的一个非常酷的功能是在绘图中添加图层列表。有趣的是，我可以将图层列表作为参数传递给函数，并将其添加到绘图中。然后，我可以得到所需的绘图外观，而不必从函数中返回绘图（这是否是个好主意是另一回事，但有可能）。

One really cool feature from the ggplot2 package that I never really exploited enough was adding lists of layers to a plot. The fun thing about this was that I could pass a list of layers as an argument to a function and have them added to the plot. I could then get the desired appearance of the plot without necessarily returning the plot from the function (whether or not this is a good idea is another matter, but it was possible).

library(ggplot2)
x <- ggplot(mtcars,
            aes(x = qsec,
                y = mpg)) 

layers <- list(geom_point(),
               geom_line(),
               xlab("Quarter Mile Time"),
               ylab("Fuel Efficiency"))

x + layers

是否可以使用管道执行此操作？类似于以下内容：

Is there a way to do this with pipes? Something akin to:

#* Obviously isn't going to work
library(dplyr)
action <- list(group_by(am, gear),
               summarise(mean = mean(mpg),
                         sd = sd(mpg)))

mtcars %>% action

推荐答案

要构造一系列magrittr步骤，请从。

To construct a sequence of magrittr steps, start with .

action = . %>% group_by(am, gear) %>% summarise(mean = mean(mpg), sd = sd(mpg))

然后可以按照OP中的想象使用它：

Then it can be used as imagined in the OP:

mtcars %>% action

就像列表一样，我们可以将其子集为查看每个步骤：

Like a list, we can subset to see each step:

action[[1]]
# function (.) 
# group_by(., am, gear)

要查看所有步骤，请使用 functions（action ）或只需键入名称：

To review all steps, use functions(action) or just type the name:

action
# Functional sequence with the following components:
# 
#  1. group_by(., am, gear)
#  2. summarise(., mean = mean(mpg), sd = sd(mpg))
# 
# Use 'functions' to extract the individual functions. 

这篇关于有没有一种方法可以“遍历列表”？的文章就介绍到这了，希望我们推荐的答案对大家有所帮助，也希望大家多多支持IT屋！