ggplot绘图时如何在已有填充图例基础上新增折线线型图例

核心逻辑：ggplot2 仅会为aes()内部映射的美学属性自动生成图例，原代码中两条折线的linetype是写在aes()外的固定参数，不会触发生成图例。只需将线型映射为自定义分类，再手动匹配线型值即可。

修改后的完整代码 #

x <- c(1:3)
y1 <- c(2/28,13/35,43/65)
y2 <- c(1/2, 2/13, 5/43)
df <- data.frame(x, y1, y2)

x <- c(rep(1 , 5) , rep(2 , 5) , rep(3 , 5))
condition <- rep(c("1", "2", "3", "4", "5") , 3)
y3 <- c(1,  0,  0,  0,  0, 6,  4,  1,  0,  0, 12, 13,  5,  5,  3)
df2 <- data.frame(x, y3, condition)

cols <- c("1"="grey80","2"="grey70","3"="grey60","4"="grey50","5"="grey40")
ggplot() + 
  geom_bar(aes(fill=condition, y=y3, x=x), data=df2, position="stack", stat="identity", width = 0.5) +
  # 第一条折线：linetype映射到自定义分类名，可根据业务修改
  geom_line(mapping = aes(x = x, y = y1*50, linetype = "指标1"), data=df, size = 1, color = "black") + 
  geom_point(mapping = aes(x = x, y = y1*50), data=df, size = 2, color = "black") +
  geom_text(aes(x=x, y=y1*50, label = round(y1, 3)), data=df, vjust = "outward", hjust = "outward",show.legend = FALSE, color="black") +
  # 第二条折线：linetype映射到第二个自定义分类名
  geom_line(mapping = aes(x = x, y = y2*50, linetype = "指标2"), data=df, size = 1, color = "black") +
  geom_point(mapping = aes(x = x, y = y2*50), data=df, size = 2, color = "black") +
  geom_text(aes(x=x, y=y2*50, label = round(y2, 3)), data=df, vjust = "outward", hjust = "outward",show.legend = FALSE, color="black") +
  scale_y_continuous(name = "Number of cases", sec.axis = sec_axis(~./50, name = "Percentage")) +
  scale_x_continuous(breaks = 1:3, labels=c("2008-2011","2012-2015","2016-2019")) + xlab(NULL) +
  scale_fill_manual(name = "Resection Index",values = cols) +
  # 新增：手动配置线型图例的名称和对应线型
  scale_linetype_manual(name = "折线指标", values = c("指标1" = 1, "指标2" = 2)) +
  # 可选：让线型图例同时显示点标记，和图中样式一致
  guides(linetype = guide_legend(override.aes = list(shape = 16))) +
  theme_minimal()

关键修改说明 #

• 将geom_line的linetype参数从aes()外移到aes()内，赋值自定义分类名，触发图例自动生成
• 新增scale_linetype_manual()配置，可自行修改图例名称name参数，以及两个分类对应的显示名称
• 额外优化了原代码直接用df$列名的不规范写法，改用data参数指定数据源，可读性更高

内容的提问来源于stack exchange，提问作者user13538376