dplyr和ggplot中的变量使用 [英] variable use in dplyr and ggplot

问题描述

我正在尝试使用dplyr/ggplot进行函数式编程.在R的前几周，我主要是在网上找到摘要后，反复尝试并反复尝试，但我试图更好地理解这一点，以使其更加自然.

I'm trying to sort out functional programming with dplyr/ggplot. In my first couple of weeks of R I mostly went by trial and error following snippets found on the web, but I'm trying to understand this better so it comes more natural.

我以mtcar为例:

library(tidyverse)
data <- mtcars
data$carb <- as.factor(data$carb)

我的不带变量的示例代码如下:

My sample code w/o using variables looks like this:

data %>% filter(carb != 4) %>%
ggplot() + geom_point(aes(x = mpg, y = hp, color = carb)) +
ggtitle("Explicit/no variables") 

并产生预期的结果:

我想出了如何通过变量调用大多数东西:

I figured out how to call most everything via variables:

remove_col <- "carb"
remove_val <- 4

x_value <- "mpg"
y_value <- "hp"

data %>% filter( carb != remove_val ) %>%
ggplot() + geom_point(aes_string(x = x_value, y = y_value, color = remove_col )) +
ggtitle("Variables for `geom_point with aes_string` and for value to remove from `carb`") 

这给出了与上面相同的情节:

This gives the same plot as above:

我正在努力解决的问题是如何解决碳水化合物"一栏.通过变量 remove_col 在 filter 中.我一直在浏览tidyverse.org，但在整理作用域动词，vars，cross()，...

The thing I'm struggling with is how to address the column "carb" in filter via the variable remove_col. I have been going through tidyverse.org, but I am having a hard time sorting out scoped verbs, vars, across(), ...

有两个问题:

1. 如何使用变量 remove_col 代替 filter 语句中的显式 carb ?
2. 为什么两个变量( remove_col 和 remove_val )在 filter 语句中的行为不同?

1. How do I use the variable remove_col instead of the explicit carb in the filter statement?
2. Why do the two variables (remove_col and remove_val) behave differently in the filter statement?

推荐答案

aes_string 已被弃用，现在的首选方式是使用 .data 代词，该代词也可以是在 filter 中使用.

aes_string has been deprecated and the preferred way now is to use .data pronoun which can also be used in filter.

library(dplyr)
library(ggplot2)

remove_col <- "carb"
remove_val <- 4

x_value <- "mpg"
y_value <- "hp"

data %>% 
  filter(.data[[remove_col]] != remove_val ) %>%
  ggplot() + geom_point(aes(x = .data[[x_value]], y = .data[[y_value]],
                        color = .data[[remove_col]])) +
  ggtitle("Variables for `geom_point with aes` and for value to remove from `carb`") 

---

您还可以将 sym 与 !! 一起使用:

data %>% 
  filter(!!sym(remove_col) != remove_val ) %>%
  ggplot() + geom_point(aes(x = !!sym(x_value), y = !!sym(y_value), color = !!sym(remove_col))) +
  ggtitle("Variables for `geom_point with aes` and for value to remove from `carb`") 

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