如何让gganimate中连续填充图例显示为离散样式

要兼顾平滑过渡效果和离散型图例，可通过自定义图例映射+强制离散图例的方式实现：

1. 保留fill的连续型映射以触发scale_fill_continuous_sequential的平滑过渡
2. 替换数值标签为原因子名称，同时强制图例显示为离散框

修改后的代码如下：

library(tidyverse)
library(colorspace)
library(gganimate)
library(ggplot2)

set.seed(42)
SIMS <- 1e3
df <- 
    tibble(
        a = rbeta(SIMS, 600, 400),
        b = rbeta(SIMS, 650, 350)
    ) |> 
    pivot_longer(
        everything(),
        names_to = 'distribution',
        values_to = 'values'
    ) |> 
    mutate(distribution = factor(distribution, levels = c('a','b')))

df |> 
    ggplot(aes(
        x = values, 
        fill = as.integer(distribution)
        )) + 
    geom_density() + 
    colorspace::scale_fill_continuous_sequential(
        palette = "Blues 3", 
        begin = 0.1, end = .9,
        breaks = c(1,2),
        labels = c("a", "b"),  # 将数值标签替换为原分布名称
        guide = guide_legend(title = "Prior")  # 强制使用离散图例样式
        ) +
    transition_states(
        states = distribution,
        transition_length = 1,
        state_length = 1,
        wrap = TRUE)

效果说明 #

• 动画仍保留scale_fill_continuous_sequential提供的平滑颜色过渡
• 图例将显示为两个对应a、b的离散颜色框，与scale_fill_discrete的样式一致

内容的提问来源于stack exchange，提问作者Joe