ggplot2：基于数据集中变量的 facet_wrap 条带颜色

Question

有没有办法根据数据框提供的变量填充使用 facet_wrap 创建的分面条？

示例数据：

MYdata <- data.frame(fruit = rep(c("apple", "orange", "plum", "banana", "pear", "grape")), farm = rep(c(0,1,3,6,9,12), each=6), weight = rnorm(36, 10000, 2500), size=rep(c("small", "large")))

示例图：

p1 = ggplot(data = MYdata, aes(x = farm, y = weight)) + geom_jitter(position = position_jitter(width = 0.3), aes(color = factor(farm)), size = 2.5, alpha = 1) + facet_wrap(~fruit)

我知道如何更改条带的背景颜色（例如变为橙色）：

p1 + theme(strip.background = element_rect(fill="orange"))

有没有办法将MYdata中的变量size中的值传递给element_rect中的参数fill？

基本上，我希望小水果（苹果、李子、梨）的条带背景颜色为绿色，而大水果（橙、香蕉、葡萄）的背景颜色为红色，而不是所有条带的一种颜色。

Answer 1

通过一些工作，您可以将您的情节与具有正确 grobs 的虚拟 gtable 结合起来，

d <- data.frame(fruit = rep(c("apple", "orange", "plum", "banana", "pear", "grape")), 
                farm = rep(c(0,1,3,6,9,12), each=6), 
                weight = rnorm(36, 10000, 2500), 
                size=rep(c("small", "large")))

p1 = ggplot(data = d, aes(x = farm, y = weight)) + 
  geom_jitter(position = position_jitter(width = 0.3), 
              aes(color = factor(farm)), size = 2.5, alpha = 1) + 
  facet_wrap(~fruit)

dummy <- ggplot(data = d, aes(x = farm, y = weight))+ facet_wrap(~fruit) + 
  geom_rect(aes(fill=size), xmin=-Inf, xmax=Inf, ymin=-Inf, ymax=Inf) +
  theme_minimal()

library(gtable)

g1 <- ggplotGrob(p1)
g2 <- ggplotGrob(dummy)

gtable_select <- function (x, ...) 
{
  matches <- c(...)
  x$layout <- x$layout[matches, , drop = FALSE]
  x$grobs <- x$grobs[matches]
  x
}

panels <- grepl(pattern="panel", g2$layout$name)
strips <- grepl(pattern="strip_t", g2$layout$name)
g2$layout$t[panels] <- g2$layout$t[panels] - 1
g2$layout$b[panels] <- g2$layout$b[panels] - 1

new_strips <- gtable_select(g2, panels | strips)
grid.newpage()
grid.draw(new_strips)

gtable_stack <- function(g1, g2){
  g1$grobs <- c(g1$grobs, g2$grobs)
  g1$layout <- transform(g1$layout, z= z-max(z), name="g2")
  g1$layout <- rbind(g1$layout, g2$layout)
  g1
}
## ideally you'd remove the old strips, for now they're just covered
new_plot <- gtable_stack(g1, new_strips)
grid.newpage()
grid.draw(new_plot)

Answer 2

您可以找到此问题的更新答案here。

g <- ggplot_gtable(ggplot_build(p))
stripr <- which(grepl('strip-r', g$layout$name))
fills <- c("red","green","blue","yellow")
k <- 1
for (i in stripr) {
  j <- which(grepl('rect', g$grobs[[i]]$grobs[[1]]$childrenOrder))
  g$grobs[[i]]$grobs[[1]]$children[[j]]$gp$fill <- fills[k]
  k <- k+1
}
grid::grid.draw(g)

Answer 3

我很想知道如何做到这一点，这是个好主意。一个想法是用不同的颜色独立生成每个图表，然后使用多图或视口之类的东西并排显示 - 这需要更多的工作。

如果您想提取此方法所需的图例 - 这是我不久前发现的 Hadley 的一些代码

g_legend<-function(a.gplot){
  tmp <- ggplot_gtable(ggplot_build(a.gplot))
  leg <- which(sapply(tmp$grobs, function(x) x$name) == "guide-box")
  legend <- tmp$grobs[[leg]]
  return(legend)}

看看它是如何从图表 p 中提取出来的，然后我把它从图中取出 图例

然后你最终绘制它

grid.newpage()
vp <- viewport(width = 1, height = 1)
#print(p, vp = vp)

submain <- viewport(width = 0.9, height = 0.9, x = 0.5, y = 1,just=c("center","top"))
print(p, vp = submain)
sublegend <- viewport(width = 0.5, height = 0.2, x = 0.5, y = 0.0,just=c("center","bottom"))
print(arrangeGrob(legend), vp = sublegend)

祝你好运

Answer 4

这不是直接为您的构面着色，而是在这里您有另一个（非常快速和简单）的解决方案，基于两个变量（size ~ fruit）而不是一个（~ fruit）的构面：

ggplot(data = MYdata, aes(x = farm, y = weight)) + 
  geom_jitter(position = position_jitter(width = 0.3), 
      aes(color = factor(farm)), size = 2.5, alpha = 1) + 
  facet_wrap(size ~ fruit)