r - 用组名及其方程标记 ggplot，可能用 ggpmisc？

Question

我想标记我的绘图，可能使用 ggpmisc 中的方程式方法来提供链接到颜色和方程式的信息标签(然后我可以完全删除图例)。例如，在下图中，理想情况下，方程 LHS 中的因子水平为 4、6 和 8。

library(tidyverse)
library(ggpmisc)

df_mtcars <- mtcars %>% mutate(factor_cyl = as.factor(cyl))

p <- ggplot(df_mtcars, aes(x = wt, y = mpg, group = factor_cyl, colour= factor_cyl))+
  geom_smooth(method="lm")+
  geom_point()+
  stat_poly_eq(formula = my_formula,
               label.x = "centre",
               #eq.with.lhs = paste0(expression(y), "~`=`~"),
               eq.with.lhs = paste0("Group~factor~level~here", "~Cylinders:", "~italic(hat(y))~`=`~"),
               aes(label = paste(..eq.label.., sep = "~~~")), 
               parse = TRUE)
p

有一个变通方法，就是之后使用描述的技术修改图表 here , 但肯定有更简单的东西吗？

p <- ggplot(df_mtcars, aes(x = wt, y = mpg, group = factor_cyl, colour= factor_cyl))+
  geom_smooth(method="lm")+
  geom_point()+
  stat_poly_eq(formula = my_formula,
               label.x = "centre",
               eq.with.lhs = paste0(expression(y), "~`=`~"),
               #eq.with.lhs = paste0("Group~factor~level~here", "~Cylinders:", "~italic(hat(y))~`=`~"),
               aes(label = paste(..eq.label.., sep = "~~~")), 
               parse = TRUE)
p

# Modification of equation LHS technique from:
# https://stackoverflow.com/questions/56376072/convert-gtable-into-ggplot-in-r-ggplot2
temp <- ggplot_build(p)
temp$data[[3]]$label <- temp$data[[3]]$label %>% 
  fct_relabel(~ str_replace(.x, "y", paste0(c("8","6","4"),"~cylinder:", "~~italic(hat(y))" )))
class(temp)

#convert back to ggplot object
#https://stackoverflow.com/questions/56376072/convert-gtable-into-ggplot-in-r-ggplot2
#install.packages("ggplotify")
library("ggplotify")
q <- as.ggplot(ggplot_gtable(temp))
class(q)
q

Answer 1

第一个示例将标签放在等式的右侧，并且部分是手动的。另一方面，编码非常简单。这之所以有效，是因为 group 始终存在于 data 中，正如层函数(统计和 geom)所见。

library(tidyverse)
library(ggpmisc)

df_mtcars <- mtcars %>% mutate(factor_cyl = as.factor(cyl))

my_formula <- y ~ x

p <- ggplot(df_mtcars, aes(x = wt, y = mpg, group = factor_cyl, colour = factor_cyl)) +
  geom_smooth(method="lm")+
  geom_point()+
  stat_poly_eq(formula = my_formula,
               label.x = "centre",
               eq.with.lhs = "italic(hat(y))~`=`~",
               aes(label = paste(stat(eq.label), "*\", \"*", 
                                 c("4", "6", "8")[stat(group)], 
                                 "~cylinders.",  sep = "")),
               label.x.npc = "right",
               parse = TRUE) +
  scale_colour_discrete(guide = FALSE)
p

事实上，通过一点点额外的杂耍，几乎可以得到问题的答案。我们需要通过将 lhs 显式粘贴到 aes() 中来添加它，这样我们就可以根据计算变量在其左侧添加粘贴文本。

library(tidyverse)
library(ggpmisc)

df_mtcars <- mtcars %>% mutate(factor_cyl = as.factor(cyl))

my_formula <- y ~ x

p <- ggplot(df_mtcars, aes(x = wt, y = mpg, group = factor_cyl, colour = factor_cyl)) +
  geom_smooth(method="lm")+
  geom_point()+
  stat_poly_eq(formula = my_formula,
               label.x = "centre",
               eq.with.lhs = "",
               aes(label = paste("bold(\"", c("4", "6", "8")[stat(group)], 
                                 " cylinders:  \")*",
                                 "italic(hat(y))~`=`~",
                                 stat(eq.label),
                                 sep = "")),
               label.x.npc = "right",
               parse = TRUE) +
  scale_colour_discrete(guide = FALSE)
p