ggplot2使用geom_ribbon实现两类周期区域分开展示问题咨询

报错原因 #

geom_ribbon要求单个分组内的填充、颜色等美学属性不能发生变化，直接将type作为分组参数时，同一个分组内会出现属性跳变，因此触发报错。

修复步骤 #

1. 调整数据预处理逻辑，新增连续同类型阶段的唯一ID #

在生成fake_data的阶段新增segment_id字段，每遇到一次type（扩张/收缩）切换，ID就加1，保证每个连续的同类型阶段对应唯一的分组ID：

library(tidyverse)
library(ggspectra)

fake_data <- tibble(
        time = seq(1,100, length.out = 1000),
        gdp  = time+time*(1-sin(0.15*time))
) %>% mutate(
        time  = row_number(),
        growth = (gdp - lag(gdp))/lag(gdp) * 100,
        peak   = as.numeric(near(gdp, peaks(gdp), tol = 0.01)),
        valley = as.numeric(near(gdp, valleys(gdp), tol = 0.01)),
        type = as.factor(
                case_when(
                        gdp >= lag(gdp) ~ "Expansion",
                        gdp <= lag(gdp) ~ "Contraction"
                )
        )
) %>% mutate(
        cycle = as.factor(cumsum(peak + valley)),
        # 新增连续同类型阶段ID
        segment_id = cumsum(type != lag(type, default = first(type)))
) %>%  na.omit()

2. 修改绘图代码，将segment_id作为ribbon的分组参数 #

fake_data %>% 
        ggplot(mapping = aes(x = time, y = gdp)) + 
        geom_line() + 
        geom_point(
                data = fake_data %>% filter(peak == 1 | valley == 1),
                mapping = aes(x = time, y = gdp),
                size = 2
        ) + 
        # group映射为segment_id，每个连续阶段单独作为一个ribbon
        geom_ribbon(aes(ymax = gdp, ymin = 0, fill = type, group = segment_id), alpha = 0.5)

效果图 #

内容的提问来源于stack exchange，提问作者Serkan