ggplot中自定义发散颜色渐变的标签

Question

我想绘制一些数据，其中我使用自定义转换来实现不同的色阶。如此处所示，标签有时或有时根本没有。我希望标签被舍入并显示颜色代表的值，而不是转换。

我已经能够成功地将其应用于非负面规模，并且我认为它与inverse中的否定数字或trans_new来电有关，我不会这样做从文档中可以理解：

以下是我探讨过的一些链接：

R: custom ggplot2 color-transform gives error in labels

GGplot custom scale transformation with custom ticks

https://github.com/tidyverse/ggplot2/issues/980看起来很有帮助

library(scales)
library(tidyverse)

log_both <- function(x){ifelse(x == 0, 0, log(abs(x)) * sign(x))}

log_both_trans <- 
  function(){
    trans_new(name = 'log_both', 
              transform = log_both,
              inverse = log_both) #not clear what `inverse` does
  }

df <-
  tibble(y = (-10:10),
         x = (y^4)*sign(y))

ggplot(df) +
  #no transformation
    geom_point(aes(factor(x), y = 1, fill = x), shape = 21, size = 10) +
    scale_fill_gradient2(low = "blue", mid = "white", high = "red") +
  #transformed
    geom_point(aes(factor(x), y = - 1, color = x), size  = 10) +
    scale_color_gradient2(low = "blue", mid = "white", high = "red", trans = "log_both") +
  ylim(-2, 2) +
  labs(colour = "transformed", fill = "default", x = "", y = "")

Answer 1

参数inverse采用的函数是原始变换的数学逆。如果你记录变换，逆是指数。需要反函数来计算与所选中断对应的标签。 （您进行对数转换以获取缩放数据，然后进行逆变换以获取标签。另请参阅this SO post.）

library(scales)
library(tidyverse)

log_both <- function(x){ifelse(x == 0, 0, log(abs(x)) * sign(x))}
exp_both <- function(x){exp(abs(x)) * sign(x)} # this is the inverse of log_both

log_both_trans <- 
  function(){
    trans_new(name = 'log_both', 
              transform = log_both,
              inverse = exp_both)
  }

df <-
  tibble(y = (-10:10),
         x = (y^4)*sign(y))

ggplot(df) +
  #no transformation
  geom_point(aes(factor(x), y = 1, fill = x), shape = 21, size = 10) +
  scale_fill_gradient2(low = "blue", mid = "white", high = "red",
                       guide = guide_colorbar(order = 1)) +
  #transformed
  geom_point(aes(factor(x), y = - 1, color = x), size  = 10) +
  scale_color_gradient2(low = "blue", mid = "white", high = "red",
                        trans = "log_both",
                        breaks = c(-10000, -100, 0, 100, 10000), # desired breaks on transformed scale
                        guide = guide_colorbar(order = 2)) +
  ylim(-2, 2) +
  labs(colour = "transformed", fill = "default", x = "", y = "")

行guide = guide_colorbar(order = 1)和guide = guide_colorbar(order = 2)只是为了确保图例以正确的顺序显示。否则它们会以随机顺序出现。