r - 如何更改单个 facet_wrap 面板的格式？

Question

是否可以更改单个分面图的格式？例如，使用下面的示例代码，可以更改 cyl=8 绘图的标题或背景颜色吗？

library(ggplot2)
ggplot(mtcars, aes(x=gear)) + 
  geom_bar(aes(y=gear), stat="identity", position="dodge") +
  facet_wrap(~cyl)

Answer 1

您可以修改 ggplot2 grobs，例如:

library("ggplot2")
d <- ggplot(mtcars, aes(x=gear)) + 
       geom_bar(aes(y=gear), stat="identity", position="dodge") +
       facet_wrap(~cyl)

grob <- ggplotGrob(d)
strip_bg <- grid.ls(getGrob(grob, "strip.background.rect",
                            grep=TRUE, global=TRUE))$name
panel_bg <- grid.ls(getGrob(grob, "panel.background.rect",
                            grep=TRUE, global=TRUE))$name
strip_text <- grid.ls(getGrob(grob, "strip.text.x",
                              grep=TRUE, global=TRUE))$name
grob <- geditGrob(grob, strip_bg[2], gp=gpar(fill="gray60"))
grob <- geditGrob(grob, panel_bg[2], gp=gpar(fill="darkolivegreen2"))
grob <- geditGrob(grob, strip_text[2], gp=gpar(col="white"))
grid.draw(grob)

更新 :这应该适用于 ggplot2 0.9.3

grob <- ggplotGrob(d)

elem <- grob$grobs$panel2
panel_bg <- grid.ls(getGrob(elem, "panel.background.rect", grep=TRUE))$name
grob$grobs$panel2 <- editGrob(elem, panel_bg, gp=gpar(fill="darkolivegreen"), grep=TRUE)

elem <- grob$grobs$strip_t.1
strip_bg <- grid.ls(getGrob(elem, "strip.background.rect", grep=TRUE))$name
grob$grobs$strip_t.1 <- editGrob(elem, strip_bg, gp=gpar(fill="gray60"), grep=TRUE)

elem <- grob$grobs$strip_t.1
strip_text <- grid.ls(getGrob(elem, "strip.text.x.text", grep=TRUE))$name
grob$grobs$strip_t.1 <- editGrob(elem, strip_text, gp=gpar(col="white"), grep=TRUE)

grid.draw(grob)