在ggplot2中通过对比度改变堆积颜色

Question

我有一个类似于以下内容的更大数据集：

example = data.frame(
  person = c(1,1,1, 2,2,2, 3,3,3),
  score =  c(5,1,2, 3,5,1, 1,2,2),
  round =  c(1,2,3, 1,2,3, 1,2,3)
)

我试图绘制它，以便每个人都有自己的颜色，并且堆叠中的任何条形都像渐变一样。我最接近的是允许alpha改变一轮：

library(ggplot2)
ggplot(data = example,
       aes(x = reorder(person, score),
           y = score,
           fill = factor(person),
           alpha = as.integer(round))) + 
  geom_col()

如何通过对比改变颜色而不是创建一个合适的渐变？

Answer 1

你可以做到

ggplot(data = example, aes(x = reorder(person, score), y = score, 
  fill = interaction(person, as.integer(round)))) + geom_col()

然后使用scale_fill_manual定义颜色值以定义渐变。

修改

简单的例子：

colornames = sort(levels(interaction(example$person, as.integer(example$round))))
colors = c(
  paste0("red", 1:3),
  paste0("green", 1:3),
  paste0("blue", 1:3)
)

ggplot(data = example, aes(x = reorder(person, score), y = score, 
  fill = interaction(person, as.integer(round)))) + geom_col() +
  scale_fill_manual(values = setNames(colors, colornames))

如果您有很多人或轮次，您可能希望使用colorRamp或rgb以编程方式设置颜色。

编辑2

或者使用半透明白柱来破解它：

ggplot(data = example, aes(x = reorder(person, score), y = score, fill = factor(person))) + 
  geom_col() + geom_col(aes(alpha = as.integer(round)), fill = "white") +
  scale_alpha(NULL, guide = FALSE, range = c(0, 0.4))

Answer 2

这里的诀窍（受@mikeck启发）是在原始透明度下创建纯色条：

ggplot(data = example, aes(x = reorder(person, score), y = score)) + 
  # Base bar color (black is another good color to try)
  geom_col(fill = "white") +
  # Overlay with the colored transparency
  geom_col(aes(fill = factor(person), alpha = round))