R ggplot2:更改小平面条中的字体和背景颜色吗? [英] R ggplot2: change colour of font and background in facet strip?

问题描述

我正在尝试自定义包含构面的ggplot2图，并希望更改构面条的颜色以及字体的颜色.我找到了一些代码来更改strip.background颜色，但无法修改它也可以更改字体颜色...知道吗?

I am trying to customize a ggplot2 plot containing facets, and would like to change both the colour of the facet strip, as well as the colour of the font. I found some code to change the strip.background colour, but was not able to modify it to change also the font color... any idea?

我到目前为止所得到的:

What I got so far:

library(ggplot2)
library(grid)

p <- ggplot(mpg, aes(displ, cty)) + geom_point() + facet_grid(drv ~ cyl) +
  ggtitle("How to change coloour of font in facet strip?")

g <- ggplot_gtable(ggplot_build(p))
strip_both <- which(grepl('strip-', g$layout$name))
fills <- c("red","green","blue","yellow","red","green","blue","yellow")
k <- 1

for (i in strip_both) {
  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.draw(g)

^{由 reprex程序包(v0.2.1)创建于2018-11-23}

推荐答案

另一种选择是使用grid的编辑功能，前提是我们要构建要编辑的每个grob的gPath.

Another option is using grid's editing functions, provided that we build the gPath of each grob that we want to edit.

准备gPath:

library(ggplot2)
library(grid)

p <- ggplot(mpg, aes(displ, cty)) + geom_point() + facet_grid(drv ~ cyl)

# Generate the ggplot2 plot grob
g <- grid.force(ggplotGrob(p))
# Get the names of grobs and their gPaths into a data.frame structure
grobs_df <- do.call(cbind.data.frame, grid.ls(g, print = FALSE))
# Build optimal gPaths that will be later used to identify grobs and edit them
grobs_df$gPath_full <- paste(grobs_df$gPath, grobs_df$name, sep = "::")
grobs_df$gPath_full <- gsub(pattern = "layout::", 
                            replacement = "", 
                            x = grobs_df$gPath_full, 
                            fixed = TRUE)

检出表grobs_df，并熟悉其命名和路径.例如，所有带都包含关键字"strip".其背景由关键字"background"标识，标题文本由"titleGrob"& 文本".然后，我们可以使用正则表达式来捕获它们:

Check out the table grobs_df and get familiar with the naming and paths. For example all strips contain the key word "strip". Their background is identified by the key word "background" and their title text by "titleGrob" & "text". We can then use regular expression to catch them:

# Get the gPaths of the strip background grobs
strip_bg_gpath <- grobs_df$gPath_full[grepl(pattern = ".*strip\\.background.*", 
                                            x = grobs_df$gPath_full)]
strip_bg_gpath[1] # example of a gPath for strip background 
## [1] "strip-t-1.7-5-7-5::strip.1-1-1-1::strip.background.x..rect.5374"

# Get the gPaths of the strip titles
strip_txt_gpath <- grobs_df$gPath_full[grepl(pattern = "strip.*titleGrob.*text.*", 
                                             x = grobs_df$gPath_full)]
strip_txt_gpath[1] # example of a gPath for strip title
## [1] "strip-t-1.7-5-7-5::strip.1-1-1-1::GRID.titleGrob.5368::GRID.text.5364"

现在我们可以编辑怪胎了

Now we can edit the grobs:

# Generate some color
n_cols <- length(strip_bg_gpath)
fills <- rainbow(n_cols)
txt_colors <- gray(0:n_cols/n_cols)

# Edit the grobs
for (i in 1:length(strip_bg_gpath)){
  g <- editGrob(grob = g, gPath = strip_bg_gpath[i], gp = gpar(fill = fills[i]))
  g <- editGrob(grob = g, gPath = strip_txt_gpath[i], gp = gpar(col = txt_colors[i]))
}

# Draw the edited plot
grid.newpage(); grid.draw(g)
# Save the edited plot
ggsave("edit_strips_bg_txt.png", g)

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