颜色渐变线为轴

Question

如何在 ggplot 中获得一条颜色渐变（最好有多个停止点）作为 (y) 轴的线？

我想将此作为颜色编码的评估提示添加到小提琴图。 “好”将编码为绿色，而“坏”应编码为红色。

我想出的是在旁边添加一个geom_segment，但这还行不通：

• 没有渐变颜色，只有一种颜色，从给定范围内随机选择
  （在这种情况下是一些浅绿色）
• 将轴手动设置为一条线感觉不对 - 应该有一些自动的东西

R 代码：

# create some test data
type_list <- c("first", "second", "third")
test_data <- data.frame()

N <- 16
for( i in 1:length(type_list))
{
    test_data = rbind( test_data,
                       data.frame(
                           idx  = 1:N,
                           vals = runif( n = N, min = 0, max = 1),
                           type = type_list[i]
                       )
   )
}

# plot data as violin 
ggplot( test_data, aes( y = vals, fill = type)) +
    geom_violin( aes( x = type )) +
    geom_segment( aes(x = 0, xend = 0, y = 0, yend = 1, color = vals, size = 2))+
    scale_colour_gradientn( colours = c( "darkred", "yellow", "darkgreen"),
                            breaks  = c( 0, 0.5, 1),
                            labels  = c( "bad", "medium", "good"),
                            limits  = c( 0,1)) + 
    guides( size = FALSE, colour = guide_legend( title="Evaluation", reverse = TRUE, 
                                                 override.aes = list( size = 5)))

Answer 1

geom_segment 在这里不工作

ggplot( test_data, aes( y = vals)) +
  geom_violin( aes( x = type, fill = type )) +
  geom_line(data = data.frame(x = c(rep(0,100)), y = seq(0,1,length.out=100)), aes(x=x, y=y, color=y),size=2)+
  scale_colour_gradientn( colours = c( "darkred", "yellow", "darkgreen"),
                          breaks  = c( 0, 0.5, 1),
                          labels  = c( "bad", "medium", "good"),
                          limits  = c( 0,1)) + 
  guides( size = FALSE, colour = guide_legend( title="Evaluation", reverse = TRUE, 
                                               override.aes = list( size = 5)))