增加`emmeans`比较箭头的粗细

Question

我正在寻找一种巧妙的方法来增加箭头的厚度。我的粗略想法是geom_line(aes(size = 5))。我得到的不是更粗的箭，而是一个新的传奇。

如何更改我的代码？非常感谢。

 warp.lm <- lm(breaks ~ wool * tension, data = warpbreaks)
 warp.emm <- emmeans(warp.lm, ~ tension | wool)
plot(warp.emm, by = NULL, comparisons = TRUE, adjust = "mvt", 
   horizontal = FALSE, colors = c("darkgreen")) +
  geom_line(aes(size = 5))

此代码 geom_line(arrow(size = 5)) 返回错误：Error in arrow(size = 5) : unused argument (size = 5)

如何更改我的代码？非常感谢。

Answer 1

首先，您是一个图例，因为您映射到 size aes 而不是使用大小作为参数，即在 aes() 之外。其次，由于 arrow() 没有 size 参数，您会收到错误消息。请参阅?arrow。

相反，您可以像这样增加箭头的大小：

library(emmeans)
library(ggplot2)
warp.lm <- lm(breaks ~ wool * tension, data = warpbreaks)
warp.emm <- emmeans(warp.lm, ~ tension | wool)
g <- plot(warp.emm, by = NULL, comparisons = TRUE, adjust = "mvt", 
     horizontal = FALSE, colors = c("darkgreen"))

检查 ggplot 对象，我们看到它由五层组成，其中箭头通过 geom_segment 层 3 和 4 绘制：

g$layers
#> [[1]]
#> geom_point: na.rm = FALSE
#> stat_identity: na.rm = FALSE
#> position_identity 
#> 
#> [[2]]
#> mapping: xend = ~ucl, yend = ~pri.fac, x = ~lcl, y = ~pri.fac 
#> geom_segment: arrow = NULL, arrow.fill = NULL, lineend = butt, linejoin = round, na.rm = FALSE
#> stat_identity: na.rm = FALSE
#> position_identity 
#> 
#> [[3]]
#> mapping: xend = ~lcmpl, yend = ~pri.fac, x = ~the.emmean, y = ~pri.fac 
#> geom_segment: arrow = list(angle = 30, length = 0.07, ends = 2, type = 2), arrow.fill = NULL, lineend = butt, linejoin = round, na.rm = FALSE
#> stat_identity: na.rm = FALSE
#> position_identity 
#> 
#> [[4]]
#> mapping: xend = ~rcmpl, yend = ~pri.fac, x = ~the.emmean, y = ~pri.fac 
#> geom_segment: arrow = list(angle = 30, length = 0.07, ends = 2, type = 2), arrow.fill = NULL, lineend = butt, linejoin = round, na.rm = FALSE
#> stat_identity: na.rm = FALSE
#> position_identity 
#> 
#> [[5]]
#> geom_point: na.rm = FALSE
#> stat_identity: na.rm = FALSE
#> position_identity

因此，要增加箭头的粗细，您可以像这样设置这些层的 size 参数：

g$layers[[3]]$aes_params$size = 1.5
g$layers[[4]]$aes_params$size = 1.5

g

^{由 reprex package (v2.0.0) 于 2021 年 5 月 30 日创建}