如何基于两个不同DataFrame使用ggplot绘制折线图？

我有两个DataFrame：
decils_general：

structure(list(grup_CNAE_Red = c("Total", "Total", "Total", "Total", 
"Total", "Total", "Total", "Total", "Total", "Total"), variable = structure(1:10, levels = c("decil1_inflacio", 
"decil2_inflacio", "decil3_inflacio", "decil4_inflacio", "decil5_inflacio", 
"decil6_inflacio", "decil7_inflacio", "decil8_inflacio", "decil9_inflacio", 
"decil10_inflacio"), class = "factor"), value = c(9.3, 8.9, 8.6, 
8.4, 8.4, 8.4, 8.2, 8.1, 8.2, 7.8)), row.names = c(NA, -10L), class = "data.frame")

以及decils_primera：

structure(list(grup_despesa_DGAPE = c("Total", "Total", "Total", 
"Total", "Total", "Total", "Total", "Total", "Total", "Total"
), variable = structure(1:10, levels = c("decil1_inflacio", "decil2_inflacio", 
"decil3_inflacio", "decil4_inflacio", "decil5_inflacio", "decil6_inflacio", 
"decil7_inflacio", "decil8_inflacio", "decil9_inflacio", "decil10_inflacio"
), class = "factor"), value = c(5.8, 5.7, 5.6, 5.3, 5, 4.9, 4.8, 
4.4, 4.4, 3.9)), row.names = c(NA, -10L), class = "data.frame")

我想绘制一张折线图，以variable为X轴、value为Y轴，样式为两条折线分别对应两个数据集（带清晰标识）。尝试了以下代码但未成功：

plot_decils_general_primera <- ggplot() +
  geom_line(data = decils_general, aes(x=variable, y=value)) +
  geom_line(data = decils_primera, aes(x=variable, y=value))

代码未生效的核心原因：

• X轴的variable是因子类型，绘制折线图时未明确分组映射，导致线条无法正确连接和区分
• 两个数据集分开绘制时缺少统一的分组标识，不利于图例生成和样式美化

推荐方案：合并数据集为长格式绘制 #

这种方式更符合ggplot的语法逻辑，便于后续调整：

1. 整理数据

   library(tidyverse)
   
   # 给数据集添加分组标签
   decils_general <- decils_general %>% mutate(group = "总体通胀")
   decils_primera <- decils_primera %>% mutate(group = "第一类支出通胀")
   
   # 合并两个数据集，并提取分位数编号优化X轴显示
   combined_data <- bind_rows(decils_general, decils_primera) %>%
     mutate(decil = as.integer(str_extract(variable, "\\d+")))
   

2. 绘制折线图

   plot_decils <- ggplot(combined_data, aes(x = decil, y = value, color = group, group = group)) +
     geom_line(linewidth = 1) +
     geom_point(size = 2) + # 添加数据点匹配目标样式
     scale_x_continuous(breaks = 1:10, labels = paste0("Decil ", 1:10)) +
     scale_y_continuous(limits = c(3, 10)) +
     labs(
       x = "收入分位数",
       y = "通胀率(%)",
       title = "不同收入分位数的通胀对比",
       color = "类别"
     ) +
     theme_minimal() +
     theme(
       plot.title = element_text(hjust = 0.5, size = 14, face = "bold"),
       axis.title = element_text(size = 12),
       legend.position = "top"
     )
   
   print(plot_decils)
   

替代方案：不合并数据集直接绘制 #

如果不想合并数据，可直接给每条折线指定分组和样式：

plot_decils <- ggplot() +
  geom_line(data = decils_general, aes(x = variable, y = value, group = 1), color = "#1f77b4", linewidth = 1) +
  geom_line(data = decils_primera, aes(x = variable, y = value, group = 1), color = "#ff7f0e", linewidth = 1) +
  geom_point(data = decils_general, aes(x = variable, y = value), color = "#1f77b4", size = 2) +
  geom_point(data = decils_primera, aes(x = variable, y = value), color = "#ff7f0e", size = 2) +
  scale_x_discrete(labels = paste0("Decil ", 1:10)) +
  labs(
    x = "收入分位数",
    y = "通胀率(%)",
    title = "不同收入分位数的通胀对比"
  ) +
  theme_minimal() +
  theme(plot.title = element_text(hjust = 0.5))

内容的提问来源于stack exchange，提问作者Maria