r - 添加图层时填充和颜色图例消失

Question

我在 ggplot 对象中改变图层时发现了一个意想不到的行为。我从一个初始情节开始。

library(ggplot2)

p <-
  ggplot(iris, aes(x = Sepal.Length, y =  Sepal.Width, color = Petal.Width, size = Petal.Length)) + 
  geom_point() +
  scale_x_continuous(position = 'top') +
  scale_size_area('Size Name', max_size = 12) +
  scale_color_gradientn(
    'Color Name',
    colors = scales::brewer_pal(type = 'div')(7),
    limits = c(-3, 3),
    breaks = c(-3,  -1.5, 0 , 1.5, 3)
  ) 

print(p)

然后我决定将点层更改为具有不同形状 21 的点层。形状 21 具有填充而不是颜色。但是，我想保持其他一切不变。为了节省打字时间，我首先删除了初始点层，然后添加了新的点层。但是，我发现填充的图例在应该显示的时候没有显示。

p$layers
#> [[1]]
#> geom_point: na.rm = FALSE
#> stat_identity: na.rm = FALSE
#> position_identity



p$layers[[1]] <- NULL

p_with_name <-
  p + 
  geom_point(aes(fill = Petal.Width), shape = 21, color = 'black') +
  scale_fill_gradientn(
    'Color Name',
    colors = scales::brewer_pal(type = 'div')(7),
    limits = c(-3, 3),
    breaks = c(-3,  -1.5, 0 , 1.5, 3)
  )

print(p_with_name)

但是，当我添加没有标题的填充比例，或者使用与色标不同的标题时，它会正确显示。

p_no_name <-
  p + 
  geom_point(aes(fill = Petal.Width), shape = 21, color = 'black') +
  scale_fill_gradientn(
    colors = scales::brewer_pal(type = 'div')(7),
    limits = c(-3, 3),
    breaks = c(-3,  -1.5, 0 , 1.5, 3)
  )

print(p_no_name)

p_diff_name <-
  p + 
  geom_point(aes(fill = Petal.Width), shape = 21, color = 'black') +
  scale_fill_gradientn(
    'Diff Name',
    colors = scales::brewer_pal(type = 'div')(7),
    limits = c(-3, 3),
    breaks = c(-3,  -1.5, 0 , 1.5, 3)
  )

print(p_diff_name)


Created on 2020-05-28 by the reprex package (v0.3.0)

是否可以添加一个与色标同名的填充标尺并让它出现？这将帮助我大大简化我的代码。

Answer 1

默认情况下，ggplot2 尝试通过合并具有相同名称的不同美学的图例来最小化图例的数量，...。经过一些试验后，我发现了一种防止图例合并的技巧，并且有两个具有相同名称的“相同”图例。我只是将 NA 添加到 scale_fill_gradientn 中的中断向量，这打破了颜色和填充比例的特性，并防止图例被合并。试试这个:

library(ggplot2)

ggplot(iris, aes(x = Sepal.Length, y =  Sepal.Width, color = Petal.Width, size = Petal.Length)) + 
  geom_point() +
  scale_x_continuous(position = 'top') +
  scale_size_area('Size Name', max_size = 12) +
  scale_color_gradientn(
    'Color Name',
    colors = scales::brewer_pal(type = 'div')(7),
    limits = c(-3, 3),
    breaks = c(-3,  -1.5, 0 , 1.5, 3)
  ) + 
  geom_point(aes(fill = Petal.Width), shape = 21, color = 'black') +
  scale_fill_gradientn(
    'Color Name',
    colors = scales::brewer_pal(type = 'div')(7),
    limits = c(-3, 3),
    breaks = c(-3,  -1.5, 0 , 1.5, 3, NA)
  )

^{由 reprex package 创建于 2020-05-28 (v0.3.0)}

编辑:问题的“干净”解决方案

# clean solution
p <- ggplot(iris, aes(x = Sepal.Length, y = Sepal.Width, size = Petal.Length)) + 
  scale_x_continuous(position = 'top') +
  scale_size_area('Size Name', max_size = 12)

p +
  geom_point(aes(color = Petal.Width))  +
  scale_color_gradientn(
    'Color Name',
    colors = scales::brewer_pal(type = 'div')(7),
    limits = c(-3, 3),
    breaks = c(-3,  -1.5, 0 , 1.5, 3) 
  )

p + 
  geom_point(aes(fill = Petal.Width), color = "black", shape = 21)  +
  scale_fill_gradientn(
    'Color Name',
    colors = scales::brewer_pal(type = 'div')(7),
    limits = c(-3, 3),
    breaks = c(-3,  -1.5, 0 , 1.5, 3)
  )