主要介绍ggplot2里Legend部分设置

ggplot2提供guide_legend()设置图例^[1]，更多参数可参考。

常用设置

以下设置在theme()中配置，常规设置请参考此文。

# 图例位置与文字样式调整
legend.position = |"left", "top", "right", "bottom", "none"|
legend.text = element_text(...),
legend.title = element_text(...)

我自己绘图时还对以下内容进行设置。

图例尺寸与边距

# 图例长宽
 legend.key.size=unit(3,'mm')
 legend.key.width=unit(10,'mm')

# 图例与图的距离或两个图例之间距离
 legend.margin=margin(b = -0.3, unit='cm')

图例文字与颜色映射

对于aes()产生的图例，可以使用scale_color_identity或scale_color_manual两种方式自定义图例显示名称与颜色的映射关系^[2]

1. aes定义颜色描述，通过label指定文字描述

   ggplot(mtcars, aes(mpg, hp) ) +
        geom_point() +
        geom_smooth(method = "lm", se = FALSE, aes(color = "black") ) +
        geom_smooth(method = "lm", formula = y ~ poly(x, 2), se = FALSE, aes(color = "red")) +
        geom_smooth(method = "lm", formula = y ~ poly(x, 3), se = FALSE, aes(color = "blue")) +
        scale_color_identity(name = "Model fit",
                             breaks = c("black", "red", "blue"),
                             labels = c("Linear", "Quadratic", "Cubic"),
                             guide = "legend")

2. aes定义文字描述，通过value建立颜色映射

   ggplot(mtcars, aes(mpg, hp) ) +
     geom_point() +
     geom_smooth(method = "lm", se = FALSE, aes(color = "Linear") ) +
     geom_smooth(method = "lm", formula = y ~ poly(x, 2), se = FALSE, aes(color = "Quadratic")) +
     geom_smooth(method = "lm", formula = y ~ poly(x, 3), se = FALSE, aes(color = "Cubic")) +
     scale_color_manual(name = "Model fit",
                        breaks = c("Linear", "Quadratic", "Cubic"),
                        values = c("Cubic" = "blue", "Quadratic" = "red", "Linear" = "black"))

图例顺序

对于多个图例(size, shape, colour, alpha, fill等)，多个图例顺序调整方式如下

# nrow调节行列数，order调节多个图例的顺序
p + guides(colour = guide_legend(nrow = 1, order = 1), 
            fill = guide_legend(nrow = 1, order = 2))

Open air风玫瑰图图例Label定义

通过加入key = list(labels = c())进行定义，替换现有label^[3]。

library(openair)
windRose(mydata, ws="ws", wd="wd", breaks=c(0,1.5,3.3,5.4,7.9,10.7), 
         auto.text= FALSE, paddle = FALSE, annotate = FALSE,
         key = list(labels = c()))

Reference

1. Legend guide ↩
2. Creating legends when aesthetics are constants in ggplot2 ↩
3. Changing the legend labels in a windrose from R openair ↩