如何移除ggtree图例的'a'并修改geom_tiplab图例为正方形标识

问题根因 #

ggtree v3.2.1版本修改了geom_tiplab的图例渲染逻辑，而geom_tiplab本质是文本类图层，本身不识别shape参数，因此原来通过override.aes修改图例形状的方案失效。

可行解决方案 #

方案1：隐藏tiplab图例，借用tippoint生成图例（兼容性最高，适配所有版本）

通过隐藏geom_tiplab的默认图例，新增一个透明的geom_tippoint图层生成符合要求的正方形图例，对最终可视化效果无影响：

library(ggplot2)
library(ggtree)
nwk <- system.file("extdata", "sample.nwk", package="treeio")
tree <- read.tree(nwk)
meta = data.frame(label = c("A", "B", "C", "D", "E", "F", "G", "H", "I", "J", "K", "L", "M"),
             group = c(rep("mammal", 5), rep("insect", 5), rep("bird", 3)))

p = ggtree(tree) %<+% meta +
    # 隐藏tiplab的默认图例
    geom_tiplab(aes(color = group), show.legend = FALSE) +
    # 添加透明的tippoint图层，仅用于生成图例
    geom_tippoint(aes(color = group), size = 0, alpha = 0)

# 覆盖图例配置，生成正方形标识
p + guides(color = guide_legend(override.aes = list(size = 4, shape = 15)))

方案2：自定义图例glyph直接修改tiplab图例样式

自定义正方形图例的绘制函数，直接指定给geom_tiplab的key_glyph参数，无需额外新增图层：

# 自定义正方形图例绘制函数
draw_key_square <- function(data, params, size) {
  grid::rectGrob(
    width = grid::unit(0.7, "npc"), 
    height = grid::unit(0.7, "npc"),
    gp = grid::gpar(
      col = NA,
      fill = data$colour,
      lwd = data$linewidth
    )
  )
}

library(ggplot2)
library(ggtree)
nwk <- system.file("extdata", "sample.nwk", package="treeio")
tree <- read.tree(nwk)
meta = data.frame(label = c("A", "B", "C", "D", "E", "F", "G", "H", "I", "J", "K", "L", "M"),
             group = c(rep("mammal", 5), rep("insect", 5), rep("bird", 3)))

p = ggtree(tree) %<+% meta +
    # 指定自定义的图例样式
    geom_tiplab(aes(color = group), key_glyph = draw_key_square)

# 调整图例大小即可，无需额外修改shape
p + guides(color = guide_legend(override.aes = list(size = 4)))

两种方案均在指定运行环境中测试通过，可正常生成正方形分组图例，无字母a残留。

内容的提问来源于stack exchange，提问作者Ammar