如何为ggplot可视化添加徽标？

问题描述

我目前正在处理ggplot柱形图，并且正在尝试在右下角添加徽标。这是图表的代码：

df <- data.frame(Names = c("2001","2004","2008","2012","2018"),Value = c(47053,68117,171535,241214,234365))

p <- ggplot(df,aes(x = Names,y = Value)) + 
              geom_col(fill = "#DB4D43") + theme_classic() +
              geom_text(aes(label =  Value,y = Value + 0.05),position = position_dodge(0.9),vjust = 0)

我遵循了我在网上找到的本教程，但是由于某种原因，无论我在image_scale函数上键入什么内容，它都不允许我调整徽标的大小，并且最终看起来太小。

img <- image_read("logo.png")
img <- image_scale(img,"200")
img <- image_scale(img,"x200")
g <- rasterGrob(img)

size = unit(4,"cm")

heights = unit.c(unit(1,"npc") - size,size)
widths = unit.c(unit(1,size)
lo = grid.layout(2,2,widths = widths,heights = heights)

grid.show.layout(lo)

grid.newpage()
pushViewport(viewport(layout = lo))

pushViewport(viewport(layout.pos.row=1:1,layout.pos.col = 1:2))
print(p,newpage=FALSE)
popViewport()

pushViewport(viewport(layout.pos.row=2:2,layout.pos.col = 2:2))
print(grid.draw(g),newpage=FALSE)
popViewport()

g = grid.grab()

grid.newpage()
grid.draw(g)

rm(list=ls())

我找到了另一个教程，尝试了之后，运行它时什么也没显示。

mypng <- readpnG('logo.png')
print(mypng)

logocomp <- p + annotation_raster(mypng,ymin = 4.5,ymax= 5,xmin = 30,xmax = 35)

解决方法

您可以使用cowplot包轻松地将图像添加到使用ggplot制作的任何绘图中。我使用R徽标作为需要添加到绘图中的图像（使用magick包读取它）。使用cowplot的优点之一是，您可以轻松指定绘图和图像的大小和位置。

library(cowplot)
library(magick)

img <- image_read("Logo.png")

# Set the canvas where you are going to draw the plot and the image
ggdraw() +
  # Draw the plot in the canvas setting the x and y positions,which go from 0,0
  # (lower left corner) to 1,1 (upper right corner) and set the width and height of
  # the plot. It's advisable that x + width = 1 and y + height = 1,to avoid clipping 
  # the plot
  draw_plot(p,x = 0,y = 0.15,width = 1,height = 0.85) +
  # Draw image in the canvas using the same concept as for the plot. Might need to 
  # play with the x,y,width and height values to obtain the desired result
  draw_image(img,x = 0.85,y = 0.02,width = 0.15,height = 0.15)  

,

尝试使用grid.raster，类似于：

grid::grid.raster(img,x = 0.15,y = 0.05,width = unit(0.5,'inches'))

x和y来定义图像的位置。 调整unit()中的数字以调整图的大小。