箭头用作ggplot2中的尺寸美观

Question

我有包含矢量坐标及其特征的数据-success_rate和prop：

ex_data <- structure(list(group = c("group A", "group A", "group A", "group A", 
"group A", "group A", "group C", "group C", "group C", "group C", 
"group C", "group W", "group W", "group W", "group W", "group W"
), category = c(5, 4, 3, 2, 1, 6, 5, 1, 2, 3, 4, 1, 4, 5, 2, 
3), success_rate = c(0.816037735849057, 0.938775510204082, 0.653061224489796, 
0.985915492957746, 0.934306569343066, 1, 0.979166666666667, 0.887323943661972, 
0.319587628865979, 0.721590909090909, 0.941176470588235, 0.689320388349515, 
0.338028169014085, 0.396551724137931, 0.7375, 0.763948497854077
), x0 = c(24.5, 24.5, 23.7, 22.6, 28.6, 27.6, 27.2, 27.4, 15.7, 
25.5, 24.2, 21.4, 17.5, 9.9, 23.6, 29), y0 = c(21.2, 27.9, 96.6, 
43.9, 65.1, 71.5, 34.3, 71.2, 47.9, 88, 36, 86.9, 49.4, 41.3, 
85.6, 16.7), x1 = c(35.2, 36.5, 34, 32.9, 39.4, 40.2, 35.9, 31.6, 
63.1, 29.5, 35.9, 35.4, 61.4, 54, 37.3, 37.2), y1 = c(5.8, 33.6, 
96.8, 70, 64.8, 96.6, 7.3, 64.9, 63.1, 89.7, 38.5, 95, 59.3, 
32.2, 77.9, 12), prop = c(0.124926340601061, 0.0866234531526223, 
0.0288744843842074, 0.041838538597525, 0.0807307012374779, 0.0271066588096641, 
0.0365853658536585, 0.0541158536585366, 0.0739329268292683, 0.134146341463415, 
0.0259146341463415, 0.0787461773700306, 0.108562691131498, 0.0443425076452599, 
0.0611620795107034, 0.178134556574924)), class = c("tbl_df", 
"tbl", "data.frame"), row.names = c(NA, -16L))

我不会为将group用作尺寸美学的每个prop制作矢量图形。不幸的是，我不认为在使用箭头的情况下尺寸美学不能很好地发挥作用，因为它无法调整通常看起来很糟糕的整个箭头的大小：

ggplot(ex_data) +
  geom_segment(aes(x = x0, y = y0, xend = x1, yend = y1, color = success_rate, size = prop),
               arrow = arrow(length = unit(0.2, "cm"), ends = 'last', type = 'closed')) +
  facet_wrap(~group) +
  scale_color_viridis_c()

因此，我只想使用prop变量控制箭头的大小。不幸的是，箭头不是geom_segment美观的，控制箭头大小的唯一方法是向箭头提供单独的向量。它适合单个组使用：

ex_data %>% 
  filter(group == 'group C') %>% 
  ggplot() +
  geom_segment(aes(x = x0, y = y0, xend = x1, yend = y1, color = success_rate),
               arrow = arrow(length = unit(filter(ex_data, group == 'group C')$prop * 3, "cm"), ends = 'last', type = 'closed')) +
  facet_wrap(~group) +
  scale_color_viridis_c()

但不包含facet_wrap：

ggplot(ex_data) +
  geom_segment(aes(x = x0, y = y0, xend = x1, yend = y1, color = success_rate),
               arrow = arrow(length = unit(ex_data$prop * 3, "cm"), ends = 'last', type = 'closed')) +
  facet_wrap(~group) +
  scale_color_viridis_c()

您会注意到group C的箭头大小不再有效（例如，上方的箭头应具有最大的箭头，而最小的箭头）。我的原始数据有更多的组，创建单独的图将非常繁琐。有什么解决方法吗？

Answer 1

通常在这种情况下（例如1，2，3），我们可以为每个方面使用子数据帧。例如，

ggplot(ex_data) +
  lapply(split(ex_data, ex_data$group), function(df)
  geom_segment(data = df, aes(x = x0, y = y0, xend = x1, yend = y1, color = success_rate),
               arrow = arrow(length = unit(df$prop * 3, "cm"), ends = 'last', type = 'closed'))) +
  facet_wrap(~group) + scale_color_viridis_c()