ggplot2中图例基础：

ggplot2会自动生成图例，我们可以对图例进行删改。

library(ggplot2)

dt = data.frame(A = 1:10, B = c(2,21,6,18,9,25,13,15,10,3), C = c('A','C','A','B','C','D','A','C','D','B'))

p = ggplot(dt, aes(x = A, y = B, group = factor(1))) +

  geom_point(aes(color = C, shape = C), size = 3.8) +

  geom_line(aes(color = C), size = 0.8)

p

原始图像

1. 隐藏图例

方法一：用 guides(fill=FALSE) 隐藏由fill产生的图例，同理可以隐藏由color、shape产生的图例。

方法二：增加图层的时候把参数 show_guide 设为 FALSE，隐藏某图层的图例。

方法三：作用和方法一类似，设置 scale_fill_discrete(guide = FALSE)，可以把中间的 fill 改成 color 或者 shape，从而隐藏相应的图例。

方法三：用 theme(legend.position = “none”) 来隐藏全局图例。

library(ggplot2)

dt = data.frame(A = 1:10, B = c(2,21,6,18,9,25,13,15,10,3), C = c('A','C','A','B','C','D','A','C','D','B'))

p = ggplot(dt, aes(x = A, y = B, group = factor(1))) +

  geom_point(aes(color = C, shape = C), size = 3.8) +

  geom_line(aes(color = C), size = 0.8, show_guide = FALSE)  ##隐藏此图层产生的图例

#  + guides(fill=FALSE)  ##隐藏由fill产生的图例

#  + scale_fill_discrete(guide = FALSE)  ##隐藏由fill产生的图例

#  + theme(legend.position = "none")  ##隐藏所有图例

p

2. 隐藏图例标题

library(ggplot2)

dt = data.frame(A = 1:10, B = c(2,21,6,18,9,25,13,15,10,3), C = c('A','C','A','B','C','D','A','C','D','B'))

p = ggplot(dt, aes(x = A, y = B, group = factor(1))) +

  geom_point(aes(color = C, shape = C), size = 3.8) +

  geom_line(aes(color = C), size = 0.8)

p + guides(color=guide_legend(title=NULL))  ##对color产生的图例去掉标题

# p + theme(legend.title=element_blank())  ##把所有图例的标题去掉

3.更改图例顺序

用 scale_color_discrete，通过 breaks 参数设置图例的顺序（注意也可以把color改成fill或者shape):

library(ggplot2)

dt = data.frame(A = 1:10, B = c(2,21,6,18,9,25,13,15,10,3), C = c('A','C','A','B','C','D','A','C','D','B'))

p = ggplot(dt, aes(x = A, y = B, group = factor(1))) +

  geom_point(aes(color = C, shape = C), size = 3.8) +

  geom_line(aes(color = C), size = 0.8) +

  scale_color_discrete(breaks = c('B','C','A','D'))

p

直接将图例逆序：

p + guides(color = guide_legend(reverse=TRUE))

或者：p + scale_color_discrete(guide = guide_legend(reverse=TRUE))

或者：p + scale_color_discrete(breaks = rev(levels(dt$C)))

4. 更改图例的标签文字

library(ggplot2)

dt = data.frame(A = 1:10, B = c(2,21,6,18,9,25,13,15,10,3), C = c('A','C','A','B','C','D','A','C','D','B'))

p = ggplot(dt, aes(x = A, y = B, group = factor(1))) +

  geom_point(aes(color = C, shape = C), size = 3.8) +

  geom_line(aes(color = C), size = 0.8) +

  scale_colour_discrete(breaks = c('A','B','C','D'), labels = c('W','X','Y','Z'))

p

5. 设置图例标题和标签文字的大小、颜色

library(ggplot2)

dt = data.frame(A = 1:10, B = c(2,21,6,18,9,25,13,15,10,3), C = c('A','C','A','B','C','D','A','C','D','B'))

p = ggplot(dt, aes(x = A, y = B, group = factor(1))) +

  geom_point(aes(color = C, shape = C), size = 3.8) +

  geom_line(aes(color = C), size = 0.8) +

  theme(legend.title = element_text(color="134", size=16, face="bold")) +  ##设置标题，face="bold"加粗

  theme(legend.text = element_text(color="azure4", size = 14, face = "bold"))  ##设置标签文字

p

6. 更改图例的位置

library(ggplot2)

dt = data.frame(A = 1:10, B = c(2,21,6,18,9,25,13,15,10,3), C = c('A','C','A','B','C','D','A','C','D','B'))

p = ggplot(dt, aes(x = A, y = B, group = factor(1))) +

  geom_point(aes(color = C, shape = C), size = 3.8) +

  geom_line(aes(color = C), size = 0.8) +

  theme(legend.position = 'top')  ##同理可以取 bottom、right、left

p

不显示图例，theme(legend.position = “none”)

第一种方法属于theme主题系统，元素名legend.position，引号内可选参数有right、left、bottom，对应右、下、左

第二种方法，元素legend.position和legend.justification同时出现并且值相同，想象图例在坐标轴里，则c(0, 1)为面板左上角，c(1, 0)为面板右下角，c(0.5, 0，5)为面板中间；面板指绘图区域。

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参考：https://blog.csdn.net/Bone_ACE/article/details/47284805