为ggplot2中的每个图例分配不同的背景颜色

问题描述

此page显示了如何使用ggplot函数来处理guide_legend的多个图例，例如顺序，标题颜色。我想知道是否可以单独修改每个图例的背景颜色。谢谢！

ggplot(mpg,aes(displ,cty)) +
  # I tired to use legend.background and a list of colors in fill to individually change the color,but is it not working
  theme(legend.background=element_rect(fill=c('brown','grey','whie'))) +
  geom_point(aes(size = hwy,colour = cyl,shape = drv)) +
  guides(
    colour = guide_colourbar(order = 1),# title.theme allows individual adjustment of title color,I wonder if similar can be done for legend background color
    shape = guide_legend(order = 2,title.theme = element_text(color='green')),size = guide_legend(order = 3,label.theme=element_text(color='red'))
  )

解决方法

我认为无法将多种颜色发送到legend.background。如果这对您确实很重要，那么您可能需要在最后的情节中破解这些怪胎。这是一个无需使用任何外部程序包即可完成的小功能：

recolor_legends <- function(gg_plot,col)
{
  p2      <- ggplotGrob(gg_plot)
  grobs   <- p2$grobs[which(p2$layout$name == "guide-box")][[1]]$grobs
  legends <- grobs[sapply(grobs,function(x) any(grepl("grobs",names(x))))]
  bgs     <- lapply(legends,function(x) {
    x$grobs[x$layout$name == "background"][[1]]
  })
  bgs <- mapply(function(x,y) {x$gp$fill <- y; x},bgs,col,SIMPLIFY = FALSE)
  legends <- mapply(function(x,y){
    x$grobs[x$layout$name == "background"][[1]] <- y; x
  },legends,SIMPLIFY = FALSE)
  grobs[sapply(grobs,names(x))))] <- legends
  p2$grobs[which(p2$layout$name == "guide-box")][[1]]$grobs <- grobs
  plot(p2)
}

所以假设我有以下情节：

p <- ggplot(mpg,aes(displ,cty)) +
  geom_point(aes(size = hwy,colour = cyl,shape = drv)) +
  guides(
    colour = guide_colourbar(order = 1),shape = guide_legend(order = 2,title.theme = element_text(color = 'green')),size = guide_legend(order = 3,label.theme = element_text(color = 'red'))
  )

p

我可以做

recolor_legends(p,c("red","blue","green"))

,

这是一种实现方式，但是有点令人费解（基于this excellent post）：

# Some data
df <- data.frame(
  x = 1:10,y = 1:10,colour = factor(sample(1:3,10,replace = TRUE)),size = factor(sample(1:3,replace = TRUE)))

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

### Step 1
# Draw a plot with the colour legend
(p1 <- ggplot(data = df,aes(x=x,y=y)) +
    geom_point(aes(colour = colour)) +
    theme_bw() +
    theme(legend.position = "top",legend.background = element_rect(fill = "lightsteelblue")))

# Extract the colour legend - leg1
leg1 <- gtable_filter(ggplot_gtable(ggplot_build(p1)),"guide-box")

### Step 2
# Draw a plot with the shape legend
(p2 <- ggplot(data = df,y=y)) +
    geom_point(aes(shape = size)) +
    theme_bw() +
    theme(legend.background = element_rect(fill = "lightseagreen")))

# Extract the shape legend - leg2
leg2 <- gtable_filter(ggplot_gtable(ggplot_build(p2)),"guide-box")

# Step 3
# Draw a plot with no legends - plot
(plot <- ggplot(data = df,y=y)) +
    geom_point(aes(shape = size,colour = colour)) +
    theme_bw() +
    theme(legend.position = "none"))

### Step 4
# Arrange the three components (plot,leg1,leg2)
# The two legends are positioned outside the plot: 
# one at the top and the other to the side.
plotNew <- arrangeGrob(leg1,plot,heights = unit.c(leg1$height,unit(1,"npc") - leg1$height),ncol = 1)

plotNew <- arrangeGrob(plotNew,leg2,widths = unit.c(unit(1,"npc") - leg2$width,leg2$width),nrow = 1)

grid.newpage()
grid.draw(plotNew)

# OR,arrange one legend at the top and the other inside the plot.
plotNew <- plot + 
  annotation_custom(grob = leg2,xmin = 7,xmax = 10,ymin = 0,ymax = 4)

plotNew <- arrangeGrob(leg1,plotNew,"npc") -  leg1$height),ncol = 1)

grid.newpage()
grid.draw(plotNew)

,

您还可以使用较低级别的grid函数来编辑相关的grob。如果p是您的问题中的情节：

library(grid)

# allow the ggplot grobs to be seen by `grid` package functions
g = grid.force(ggplotGrob(p))

# grab the names of the guide grobs,to be used in gPath in `editGrob`
nms = grep("^guides",grid.ls(g,print=FALSE)$name,value=TRUE)

# edit the guide grobs by passing a vector of colours to `gpar`
for(i in seq_along(nms)) 
  g = editGrob(g,gPath("guide-box",nms[[i]],"background"),grep=TRUE,gp = gpar(fill=c("red","green")[i]))

grid.newpage(); grid.draw(g)

哪个给

,

基于Allan的回答，我增强了功能，以便按键的背景颜色现在是透明的。

ggplot.legends.recolor.fx <- function(gg_plot,col) {
  p2      <- ggplotGrob(gg_plot)
  grobs   <- p2$grobs[which(p2$layout$name == "guide-box")][[1]]$grobs
  legends <- grobs[sapply(grobs,SIMPLIFY = FALSE)
  bgs <- mapply(function(x,y) {x$gp$alpha <- y; x},0.3,SIMPLIFY = FALSE)
  
  # background color for the keys are changed to transparent below:
  key.bgs <- lapply(legends,function(x) {
    x$grobs[grepl('key.*bg',x$layout$name)]
  })    
  key.bgs <- lapply(key.bgs,function(z) {
    z <- mapply(function(x,z,SIMPLIFY = FALSE)})
  legends <- mapply(function(x,y){
    x$grobs[grepl('key.*bg',x$layout$name)] <- y; x
  },key.bgs,SIMPLIFY = FALSE)
  
  grobs[sapply(grobs,names(x))))] <- legends
  
  p2$grobs[which(p2$layout$name == "guide-box")][[1]]$grobs <- grobs
  plot(p2)
}