如何在ggplot2页脚上添加徽标

Question

如何在ggplot2的绘图区域外添加图像徽标.从'grid'包中尝试了rasterGrob函数,但是它保留了绘图区域内的图像.

这是启动脚本:

library(ggplot2)
library(png)
library(gridExtra)
library(grid)

gg <- ggplot(df1, aes(x = mpg, y = wt)) + 
       theme_minimal() +
        geom_count() + 
        labs(title = "Title Goes Here", x = "", y = "")

img <- readPNG("fig/logo.png")

这是我正在寻找的结果.

我可以在右侧添加注释,但左侧的徽标是我受到挑战的地方.

Answer 1

您可以添加元素,annotation_custom但需要关闭剪裁,以便图像在绘图区域之外显示.我稍微改变了你的例子,以使其可重复.

library(ggplot2)
library(png)
library(gridExtra)
library(grid)

gg <- ggplot(mtcars, aes(x = mpg, y = wt)) + 
  theme_minimal() +
  geom_count() + 
  labs(title = "Title Goes Here", x = "", y = "")

img = readPNG(system.file("img", "Rlogo.png", package="png"))

gg = gg + 
  annotation_custom(rasterGrob(img), 
                    xmin=0.95*min(mtcars$mpg)-1, xmax=0.95*min(mtcars$mpg)+1, 
                    ymin=0.62*min(mtcars$wt)-0.5, ymax=0.62*min(mtcars$wt)+0.5) +
  annotation_custom(textGrob("Footer goes here", gp=gpar(col="blue")), 
                    xmin=max(mtcars$mpg), xmax=max(mtcars$mpg), 
                    ymin=0.6*min(mtcars$wt), ymax=0.6*min(mtcars$wt)) +
  theme(plot.margin=margin(5,5,30,5))

# Turn off clipping
gt <- ggplot_gtable(ggplot_build(gg))
gt$layout$clip[gt$layout$name=="panel"] <- "off"
grid.draw(gt)

另一个选择是使用ggplot的caption功能来添加文本页脚,这节省了一些代码:

gg = gg + 
  annotation_custom(rasterGrob(img), 
                    xmin=0.95*min(mtcars$mpg)-1, xmax=0.95*min(mtcars$mpg)+1, 
                    ymin=0.62*min(mtcars$wt)-0.5, ymax=0.62*min(mtcars$wt)+0.5) +
  labs(caption="Footer goes here") +
  theme(plot.margin=margin(5,5,15,5),
        plot.caption=element_text(colour="blue", hjust=1.05, size=15)) 

# Turn off clipping
gt <- ggplot_gtable(ggplot_build(gg))
gt$layout$clip[gt$layout$name=="panel"] <- "off"
grid.draw(gt)