r - 垂直对齐 ggplot2 绘图

Question

使用https://gist.github.com/low-decarie/5886616中的代码 可以生成双树状图瓦片图：

dual_dendogram_tile_plot(as.matrix(USarrests), main="USA Arrests")

问题：将垂直树状图与平铺图区域对齐。（和/或改进水平树状图的对齐方式）

这个问题涉及：

左对齐两个图形边缘（ggplot）
指定ggplot2面板宽度 将相关矩阵绘制成图形

Answer 1

这是一个对齐更多基本 grobs 的示例，

library(ggplot2)
library(grid)
library(gtable)

p <- qplot(1,1)
g <- ggplotGrob(p)

panel_id <- g$layout[g$layout$name == "panel",c("t","l")]
g <- gtable_add_cols(g, unit(1,"cm"))

g <- gtable_add_grob(g, rectGrob(gp=gpar(fill="red")),
                     t = panel_id$t, l = ncol(g))

g <- gtable_add_rows(g, unit(1,"in"), 0)
g <- gtable_add_grob(g, rectGrob(gp=gpar(fill="blue")),
                     t = 1, l = panel_id$l)

grid.newpage()
grid.draw(g)

和你的grobs

Answer 2

@baptiste 的回答帮助我更好地理解了 gtable 结构以及如何修改它。下面我将我修改后的变体发布为（我自己的）重用的代码片段。

它find_panel()用于获取面板范围，并将%>%修改直接导入grid.draw. 管道大大简化了gtable_*函数的使用，因为它允许轻松取消注释单行并检查对最终绘图的影响。

library(ggplot2)
library(grid)
library(gtable)
library(dplyr)

p <- ggplot(tribble(~x,~y,~a,~b, 
                    1, 1, "a1","b1",
                    1, 1, "a2","b1",
                    1, 1, "a2","b2"), 
           aes(x=x,y=y)) + 
  geom_point() + 
  facet_grid(vars(a),vars(b))

g <- ggplotGrob(p)
panels_extent <- g %>% find_panel()
g %>%
  # Add red box to the very right, by appending a column and then filling it
  gtable_add_cols(widths = unit(1,"cm"), pos = -1) %>%
  gtable_add_grob(rectGrob(gp=gpar(fill="red")),
                  t = panels_extent$t, b = panels_extent$b,
                  l = -1, r = -1) %>%
  # Add green box to the top, by prepending a row and then filling it
  # Note the green box extends horizontally over the first panel as well 
  # as the space in between.
  gtable_add_rows(heights = unit(1,"cm"), pos = 0) %>%
  gtable_add_grob(rectGrob(gp=gpar(fill="green")),
                  t = 1, b = 1,
                  l = panels_extent$l, r = panels_extent$l+1) %>%
  {grid.newpage();grid.draw(.)}