使用geom_ridgeline_gradient时分组变量堆叠问题求助

问题 #

使用ggridges包的geom_ridgeline_gradient函数绘制带渐变效果的脊线图时，分组变量（社区）直接堆叠在一起，没有像正常脊线图那样相互分离。期望实现各社区分组分离的脊线图，按EPA指定的空气质量指数（AQI）类别颜色展示对应天数的计数。

当前绘图效果：各社区的脊线完全堆叠，无任何间距，无法区分不同社区的分组。
目标效果参考：每个社区作为独立一行，脊线之间留有明显间距，清晰展示各社区不同AQI类别的天数分布（类似ggridges官方示例中的分组分离样式）。

以下是示例数据及原始绘图代码：

library(ggridges);library(tidyverse)

#data to generate plot
AQIcounts <- data.frame(
  site_name = rep(c("community1", "community2", "community3"),6),
  AQI_description = rep(c("Good","Moderate","Unhealthy for Sensitive Groups","Unhealthy","Very Unhealthy","Hazardous"),3),
  n = c(5472, 661, 65, 78, 30, 16, 282, 23, NA, NA, NA, NA, 3945, 441, 9, 2, NA, NA)
)

#set level ordering for AQI_description
AQIcounts$AQI_description <- factor(AQIcounts$AQI_description, levels=c("Good", "Moderate", "Unhealthy for Sensitive Groups", "Unhealthy", "Very Unhealthy", "Hazardous"))

#set color assignments to factors
palette <- c("green","yellow","orange","red","purple","maroon") #create palette
names(palette) <- levels(AQIcounts$AQI_description) #set the names of color levels
ggpalette <- scale_fill_manual(name = "AQI_description", values = palette)

ggplot(AQIcounts, aes(x=AQI_description, y = site_name, height = n, group = site_name, fill = AQI_description)) +
  geom_ridgeline_gradient()  + 
  theme(axis.text.x = element_text(angle = 45, vjust = 1, hjust = 1)) + 
  ggpalette

解决方案 #

问题根源 #

1. x轴为分类变量，geom_ridgeline_gradient默认需要连续型x轴生成连贯脊线，且分类y轴默认无间距，导致各组堆叠。
2. 数据中存在NA值，造成脊线断裂，无法形成完整分组区域。
3. 未设置y轴间距扩展参数，社区分组间无留白。

修改后的代码 #

library(ggridges);library(tidyverse)

# 数据处理：替换NA为0，避免脊线断裂
AQIcounts <- data.frame(
  site_name = rep(c("community1", "community2", "community3"),6),
  AQI_description = rep(c("Good","Moderate","Unhealthy for Sensitive Groups","Unhealthy","Very Unhealthy","Hazardous"),3),
  n = c(5472, 661, 65, 78, 30, 16, 282, 23, NA, NA, NA, NA, 3945, 441, 9, 2, NA, NA)
) %>% 
  mutate(n = replace_na(n, 0)) # 替换NA为0

# 设置AQI类别顺序
AQIcounts$AQI_description <- factor(AQIcounts$AQI_description, 
                                    levels=c("Good", "Moderate", "Unhealthy for Sensitive Groups", 
                                             "Unhealthy", "Very Unhealthy", "Hazardous"))

# 定义颜色映射
palette <- c("green","yellow","orange","red","purple","maroon")
names(palette) <- levels(AQIcounts$AQI_description)
ggpalette <- scale_fill_manual(name = "AQI类别", values = palette)

# 绘图：将分类x转为数值，设置y轴间距，调整脊线缩放
ggplot(AQIcounts, aes(x = as.numeric(AQI_description), 
                      y = site_name, 
                      height = n, 
                      group = site_name, 
                      fill = AQI_description)) +
  geom_ridgeline_gradient(scale = 0.0001) + # scale参数根据数据量级调整，避免脊线过高
  # 还原x轴的分类标签
  scale_x_continuous(breaks = 1:length(levels(AQIcounts$AQI_description)),
                     labels = levels(AQIcounts$AQI_description)) +
  # 设置y轴间距，分离各组
  scale_y_discrete(expand = expansion(add = c(0.5, 0.5))) +
  theme(axis.text.x = element_text(angle = 45, vjust = 1, hjust = 1)) +
  ggpalette +
  labs(x = "AQI类别", y = "社区")

关键修改点说明 #

• 替换NA为0：用replace_na(n, 0)确保每个社区的所有AQI类别都有高度值，避免脊线断裂。
• x轴转为数值型：as.numeric(AQI_description)让geom_ridgeline_gradient生成连贯脊线，再通过scale_x_continuous还原分类标签。
• 调整y轴间距：scale_y_discrete(expand = expansion(add = c(0.5, 0.5)))给每个社区分组添加上下留白，实现分组分离。
• scale参数调整：根据数据量级调整geom_ridgeline_gradient的scale参数，避免脊线高度超出画布。

内容的提问来源于stack exchange，提问作者Kelly Ireland