如何在ggplot中应用legend.key背景透明？

Question

我使用mpgggplot2 包中的数据来测试绘图参数。我发现 lengend.key 背景（右上角，标签车辆模型）颜色可以更改为任何其他颜色，但透明或白色除外。如何将lengend键背景默认灰色更改为透明？

library(ggplot2)
p <- ggplot(data=mpg,mapping=aes(x=cty,y=hwy,colour=class))+
     geom_point(aes(size=displ),alpha=0.5)+
     stat_smooth(method='loess')+
     scale_size_continuous(range=c(4,10))+
     facet_wrap(~year,ncol=2)+
      labs(x='distance per gallon in city',y='distance per gallon in highway',
      title='fuel consumption and model',size='displacement',colour='vehicle model')

p+
theme(
    plot.background=element_rect(fill='transparent', colour='transparent'),
    panel.background=element_rect(fill='transparent', colour='gray'),
    panel.border=element_rect(fill='transparent', colour='black'),        
    axis.text=element_text(color='black'),
    panel.grid.major=element_line(colour='grey',linetype='dashed'),
    strip.background=element_rect(fill='transparent', colour='transparent'),
    panel.spacing.x=unit(4,'mm'),
    legend.box.background=element_rect(fill='blue', colour='transparent'),
    legend.key=element_rect(fill='transparent', colour='transparent')
    )

Answer 1

您需要添加se = FALSE或删除stat_smooth(method = "loess")以删除图例键中灰色填充的背景vehicle model。

library(ggplot2)

p <- ggplot(data = mpg, mapping = aes(x = cty, y = hwy, colour = class)) +
  geom_point(aes(size = displ), alpha = 0.5) +
  stat_smooth(method = "loess", se = FALSE) + # Add se = FALSE
  scale_size_continuous(range = c(4, 10)) +
  facet_wrap(~year, ncol = 2) +
  labs(
    x = "distance per gallon in city", y = "distance per gallon in highway",
    title = "fuel consumption and model", size = "displacement", colour = "vehicle model"
  )

p + 
  theme(
    plot.background = element_blank(),
    panel.background = element_rect(fill = "transparent", colour = "gray"),
    panel.border = element_rect(fill = "transparent", colour = "black"),
    axis.text = element_text(color = "black"),
    panel.grid.major = element_line(colour = "grey", linetype = "dashed"),
    strip.background = element_blank(),
    panel.spacing.x = unit(4, "mm"),
    legend.box.background = element_rect(fill = "blue", colour = "transparent"),
    legend.key = element_rect(fill = "transparent", colour = "transparent")
  )

p +
  theme(
    plot.background = element_rect(fill = "transparent", colour = "transparent"),
    panel.background = element_rect(fill = "transparent", colour = "gray"),
    panel.border = element_rect(fill = "transparent", colour = "black"),
    axis.text = element_text(color = "black"),
    panel.grid.major = element_line(colour = "grey", linetype = "dashed"),
    strip.background = element_rect(fill = "transparent", colour = "transparent"),
    panel.spacing.x = unit(4, "mm"),
    legend.background = element_blank(),
    legend.box.background = element_blank(),
    legend.key = element_blank()
  )

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