GGPLOT之后如何使用％t＆gt;％管道？

Question

让我们看一下以下两种代码：

mtcars %>%
    ggplot(aes(x = cyl, y = mpg))+
    geom_line()

这可以工作并创建以下图：

现在让我们请看一下：

mtcars %>%
    group_by(cyl) %>% 
    summarise(mpg = mean(mpg))

这也有效并创建以下输出：

# A tibble: 3 x 2
    cyl   mpg
  <dbl> <dbl>
1     4  26.7
2     6  19.7
3     8  15.1

但是，这是不起作用的：

mtcars %T>%
    ggplot(aes(x = cyl, y = mpg))+
    geom_line() %>%
    group_by(cyl) %>% 
    summarise(mpg = mean(mpg))

它给出以下错误：

Error in UseMethod("group_by") : 
  no applicable method for 'group_by' applied to an object of class "c('LayerInstance', 'Layer', 'ggproto', 'gg')"

为什么它不起作用？从％t＆gt;％文档中，我希望在ggplot mtcars将返回>。不幸的是，这似乎不起作用。我是否误解了％t＆gt;％管道？代码应该如何使这项工作看起来如何？

Answer 1

您需要将ggplot打电话给print，以便您接到两个呼叫。您可以使用以下代码：

library(tidyverse)
#> Warning: package 'ggplot2' was built under R version 4.1.2
#> Warning: package 'tibble' was built under R version 4.1.2
#> Warning: package 'tidyr' was built under R version 4.1.2
#> Warning: package 'readr' was built under R version 4.1.2
#> Warning: package 'dplyr' was built under R version 4.1.2
library(magrittr)
#> Warning: package 'magrittr' was built under R version 4.1.2
#> 
#> Attaching package: 'magrittr'
#> The following object is masked from 'package:purrr':
#> 
#>     set_names
#> The following object is masked from 'package:tidyr':
#> 
#>     extract
mtcars %T>%
  {print(ggplot(., aes(x = cyl, y = mpg))+
  geom_line())} %>%
  group_by(cyl) %>% 
  summarise(mpg = mean(mpg))

#> # A tibble: 3 × 2
#>     cyl   mpg
#>   <dbl> <dbl>
#> 1     4  26.7
#> 2     6  19.7
#> 3     8  15.1

^{在2022-06-30创建的 reprex软件包 （v2.0.1）}