Is ```summarize()``` contractive with ```ggplot()```-CodePudding

Hello everyone Here is one example code

library(palmerpenguins)
mypenguins = penguins %>% drop_na()
penguins_df <- mypenguins %>% 
  group_by(species) %>% 
  summarize(mean_g = mean(bill_length_mm)) 
penguins_df %>% 
  ggplot(aes(x = mean_g, y = species))  
  geom_col(width = 0.5)  
  theme(
    axis.text.y = element_text(
      color = if_else(penguins_df$mean_g > 48, "red", "black"), 
      face = if_else(penguins_df$mean_g  > 48, "bold", "plain"), 
      size = 20
    )
  )

However when I want to integrate two parts "summarize" and "ggplot" like this

penguins_df <- mypenguins %>% 
  group_by(species) %>% 
  summarize(mean_g = mean(bill_length_mm)) %>%
  ggplot(aes(x = mean_g, y = species))  
  geom_col(width = 0.5)  
  theme(
    axis.text.y = element_text(
      color = if_else(mean_g > 48, "red", "black"), 
      face = if_else(mean_g  > 48, "bold", "plain"), 
      size = 20
    )
  )

I was warned: "mean_g" not found, but I do define "mean_g" before, which confused me a lot. Would someone mind offering some advice kindly? Thanks.

CodePudding user response：

We can use the "trick" of surrounding the ggplot expression with curly braces. The only downside is that we'll need to explicitly refer to the piped object with a dot.

Here's the code:

library(tidyverse)
library(palmerpenguins)


mypenguins <- penguins %>% drop_na()

penguins_df <- mypenguins %>%
  group_by(species) %>%
  summarize(mean_g = mean(bill_length_mm))

penguins_df %>%
  {
    ggplot(., aes(x = mean_g, y = species))  
      geom_col(width = 0.5)  
      theme(
        axis.text.y = element_text(
          color = if_else(.$mean_g > 48, "red", "black"),
          face = if_else(.$mean_g > 48, "bold", "plain"),
          size = 20
        )
      )
  }

CodePudding user response：

Too long for a comment.

The aesthetics defined with ggplot(aes(...)), apply to geoms only, not to the theme. That's why this doesn't work.

So for instance, you can write:

mypenguins <- penguins %>% drop_na()
mypenguins %>% 
  group_by(species) %>% 
  summarize(mean_g = mean(bill_length_mm)) %>%
  ggplot(aes(x = mean_g, y = species))  
  geom_col(width = 0.5)

This will work because mean_g is an aesthetic, so ggplot looks for it in the context of the data.frame (it looks for the mean_g column). The theme(...) function does not respect aesthetics, so it looks for mean_g in the calling environment, and fails because there is not such object.