ggplot2在facet图中为两个Y轴添加单独的图例

Question

我正在尝试在轴标题旁添加图例。我按照这个stackoverflow答案来绘制图表。

如何在两个y轴上添加图例？我希望左右两个Y轴上都有图例。在下面的图表中，右Y轴缺少图例符号。

同时，是否可能给文本赋予类似于图例中符号的唯一颜色。

同时，如何将图例键符号旋转到垂直位置？

我目前拥有的代码：

## install ggplot2 as follows:
# install.packages("devtools")
# devtools::install_github("hadley/ggplot2")

packageVersion('ggplot2')
# [1] ‘2.2.0.9000’

packageVersion('data.table')
# [1] ‘1.9.7’

# libraries
library(ggplot2)
library(data.table)

# data
df1 <- structure(list(plate_num = c(1L, 2L, 3L, 4L, 5L, 6L, 7L, 8L, 9L, 10L, 11L, 12L, 13L,
                                    1L, 2L, 3L, 4L, 5L, 6L, 7L, 8L, 9L, 10L, 11L, 12L, 13L), 
                      `Before Treatment` = c(662.253098499674, 684.416067929458, 688.284595300261, 
                                             692.532637075718, 728.988910632746, 684.708496732026, 
                                             703.390706806283, 673.920966688439, 644.945573770492, 504.423076923077, 
                                             580.263743455497, 580.563767168084, 689.6014445174, 804.740789473684, 
                                             815.792020928712, 789.234139960759, 778.087753765553, 745.777922926192, 
                                             787.762434554974, 780.828758169935, 781.265839320705, 732.683552631579, 
                                             773.964052287582, 713.941253263708, 724.459070072037, 838.899148657498),
                      `After Treatment` = c(440.251141552511, 431.039190071848, 460.349216710183, 479.798955613577, 
                                            441.123939986954, 436.17908496732, 453.938481675393, 437.237753102547,
                                            448.52, 426.70925684485, 390.417539267016, 359.66121648136, 451.969796454366, 
                                            515.611842105263, 542.325703073904, 547.637671680837, 518.316306483301, 478.536903984324, 
                                            501.122382198953, 494.475816993464, 474.581319399086, 438.515789473684, 
                                            440.251633986928, 407.945822454308, 413.571054354944, 537.290111329404),
                      Ratio = c(1.50426208132996, 1.58782793698034, 1.49513580194398, 1.443380876455, 1.6525716347526, 
                                1.56978754903694, 1.54952870311901, 1.54131467812749, 1.43794161636157, 1.18212358609901, 1.48626453756382, 
                                                 1.61419619509676, 1.5257688675819, 1.5607492376201, 1.50424738548219, 
                                                 1.44116115594897, 1.50118324280547, 1.55845435684647, 1.57199610821259, 
                                                 1.57910403569899, 1.64622122149676, 1.67082593197148, 1.75800381540563, 
                                                 1.75008840381905, 1.75171608951693, 1.56135229547), 
                      grp = c("wt-3X", "wt-3X", "wt-3X", "wt-3X", "wt-3X", "wt-3X", "wt-3X", "wt-3X", "wt-3X", "wt-3X",
                              "wt-3X", "wt-3X", "wt-3X", "mu-3X", "mu-3X", "mu-3X", "mu-3X", "mu-3X", "mu-3X", "mu-3X", 
                              "mu-3X", "mu-3X", "mu-3X", "mu-3X", "mu-3X", "mu-3X")),
                 .Names = c("plate_num", "Before Treatment", "After Treatment", "Ratio", "grp"),
                 row.names = c(NA, -26L), class = "data.frame")


max1 <- max(c(df1$`Before Treatment`, df1$`After Treatment`))
max2 <- max(df1$Ratio)
df1$norm_ratio <- df1$Ratio / (max2/max1)
df1 <- melt(df1, id = c("plate_num", 'grp'))
df1$plate_num <- factor(df1$plate_num, levels = 1:13, ordered = TRUE)

# plot
p <- ggplot(mapping = aes(x = plate_num, y = value, group = variable)) +
  geom_line(data = subset(df1, variable %in% c('Before Treatment', 'After Treatment')), aes(color = variable), size = 1, show.legend = TRUE) +
  geom_point(data = subset(df1, variable %in% c('Before Treatment', 'After Treatment')), aes(color = variable), size = 2, show.legend = TRUE) +
  scale_color_manual(values = c('green', 'blue'), guide = 'legend') + 
  geom_line(data = subset(df1, variable %in% c('norm_ratio')), aes(color = variable), col = 'red', size = 1) +
  geom_point(data = subset(df1, variable %in% c('norm_ratio')), aes(color = variable), col = 'red', size = 2) +
  facet_wrap(~ grp) +
  scale_y_continuous(sec.axis = sec_axis(trans = ~ . * (max2 / max1),
                                         name = 'Ratio of Main Effect of Before and After Treatment\n')) +

  theme_bw() + 
  theme(axis.text.x = element_text(size=15, face="bold", angle = 0, vjust = 1), 
        axis.title.x = element_text(size=15, face="bold"),
        axis.text.y = element_text(size=15, face="bold", color = 'black'),
        axis.text.y.right = element_text(size=15, face="bold", color = 'red'),
        axis.title.y.right = element_text(size=15, face="bold", color = 'red'),
        axis.title.y = element_text(size=15, face="bold"),
        axis.ticks.length=unit(0.5,"cm"),
        legend.position = c(-0.28, 0.4),
        legend.direction = 'vertical',
        legend.text = element_text(size = 15, angle = 90),
        legend.key = element_rect(color = NA, fill = NA),
        legend.key.width=unit(2,"line"),
        legend.key.height=unit(2,"line"),
        legend.title = element_blank(),
        panel.grid.major = element_blank(), 
        panel.grid.minor = element_blank(),
        strip.text.x = element_text(size=15, face="bold", color = "black", angle = 0),
        plot.margin = unit(c(1,4,1,3), "cm")) +
  ylab('Main Effect of TDP43\n\n\n') + 
  xlab('\nPlate Number')

print(p)

- Sathish

---

感谢您的评论。请查看左侧y轴上的图例：图例键应该是垂直方向的，但它们被水平对齐了。 - Sathish

在代码中，我使用了 legend.direction = 'vertical'，但仍然没有效果。 - Sathish

谢谢。代码中涉及到一个名为 variable 的对象。我认为它在问题中缺失了。 - Hack-R

在 melt 函数中，我可以使用 variable.name 参数来赋予用户定义的名称。 - Sathish

在我的代码中，我提到了在这个任务中使用的库。谢谢。 - Sathish

Answer 1

为了让内容更简短，我缩减了你的主题定义。

---

我利用了你可以从ggplot元素中提取单个图形的事实。在这种情况下，我们提取3个图例。

为了得到所需的结果，我们需要创建4个图：

1.图p：没有图例的图

2.绿色图例的图l1

3.蓝色图例的图l2

4.红色图例的图l3

我们使用的函数是cowplot包的get_legend()。它允许你提取一个图的图例。

在提取了左侧的两个图例后，我们使用arrangeGrob将它们组合起来，并将组合后的图例命名为llegend。在提取了红色图例之后，我们使用grid.arrange将三个对象（llegend、p和rlegend）绘制出来。

关于图例键的方向，你应该注意到我们将图例打印在相应的图形顶部。这样我们就可以使用editGrob在提取它们后旋转（组合的）图例，使图例键具有正确的方向。

这是全部代码：

library(ggplot2)
library(gridExtra)
library(grid)
library(cowplot)

# actual plot without legends
p <- ggplot(mapping = aes(x = plate_num, y = value, group = variable)) +
  geom_line(data = subset(df1, variable %in% c('Before Treatment', 'After Treatment')), aes(color = variable), size = 1, show.legend = F) +
  geom_point(data = subset(df1, variable %in% c('Before Treatment', 'After Treatment')), aes(color = variable), size = 2, show.legend = F) +

  geom_line(data = subset(df1, variable %in% c('norm_ratio')), aes(color = 'Test'), col = 'red', size = 1) +
  geom_point(data = subset(df1, variable %in% c('norm_ratio')), aes(color = 'Test'), col = 'red', size = 2) +
  facet_wrap(~ grp) +
  scale_y_continuous(sec.axis = sec_axis(trans = ~ . * (max2 / max1),
                                         name = 'Ratio of Main Effect of Before and After Treatment\n')) +
  scale_color_manual(values = c('green', 'blue'), guide = 'legend') +
  theme_bw() + 
  theme(axis.text.x = element_text(size=11, face="bold", angle = 0, vjust = 1), 
        axis.title.x = element_text(size=11, face="bold"),
        axis.text.y = element_text(size=11, face="bold", color = 'black'),
        axis.text.y.right = element_text(size=11, face="bold", color = 'red'),
        axis.title.y.right = element_text(size=11, face="bold", color = 'red', margin=margin(0,0,0,0)),
        axis.title.y = element_text(size=11, face="bold", margin=margin(0,-30,0,0)),
        panel.grid.minor = element_blank(),
        strip.text.x = element_text(size=15, face="bold", color = "black", angle = 0),
        plot.margin = unit(c(1,1,1,1), "cm")) +
  ylab('Main Effect of TDP43\n\n\n') + 
  xlab('\nPlate Number')

# Create legend on the left 
l1 <- ggplot(mapping = aes(x = plate_num, y = value, group = variable)) +
  geom_line(data = subset(df1, variable %in% c('Before Treatment')), aes(color = variable), size = 1, show.legend = TRUE) +
  geom_point(data = subset(df1, variable %in% c('Before Treatment')), aes(color = variable), size = 2, show.legend = TRUE) +
  scale_color_manual(values = 'green', guide = 'legend') +
  theme(legend.direction = 'horizontal', 
        legend.text = element_text(angle = 0, colour = c('green', 'blue')),
        legend.position = 'top',
        legend.title = element_blank(),
        legend.margin = margin(0, 0, 0, 0, 'cm'),
        legend.box.margin = unit(c(0, 0 , -2.5 ,0), 'cm'))

l2 <- ggplot(mapping = aes(x = plate_num, y = value, group = variable)) +
  geom_line(data = subset(df1, variable %in% c('After Treatment')), aes(color = variable), size = 1, show.legend = TRUE) +
  geom_point(data = subset(df1, variable %in% c('After Treatment')), aes(color = variable), size = 2, show.legend = TRUE) +
  scale_color_manual(values = 'blue', guide = 'legend') +
  theme(legend.direction = 'horizontal', 
        legend.text = element_text(angle = 0, colour = c('blue')),
        legend.position = 'top',
        legend.title = element_blank(),
        legend.margin = margin(0, 0, 0, 0, 'cm'),
        legend.box.margin = unit(c(0, 0 , -2.5 ,0), 'cm'))

legend1 <- get_legend(l1)
legend2 <- get_legend(l2)

# Combine green and blue legend
llegend <- editGrob(arrangeGrob(grobs = list(legend1, legend2), 
                       nrow = 1, ncol = 2), vp = viewport(angle = 90))

# Plot with legend on the right
l3 <- ggplot(mapping = aes(x = plate_num, y = value, group = variable)) +
   geom_line(data = subset(df1, variable %in% c('norm_ratio')), aes(color = variable), size = 1) +
  geom_point(data = subset(df1, variable %in% c('norm_ratio')), aes(color = variable), size = 2) +
  scale_color_manual(values = 'red', guide = 'legend') +
  theme(legend.direction = 'horizontal', 
        legend.text = element_text(angle = 0, colour = 'red'),
        legend.position = 'top',
        legend.title = element_blank(),
        legend.margin = margin(0, 0, 0, 0, 'cm'),
        legend.box.margin = unit(c(0, 0, -3, 0), 'cm'))

# extract legend
rlegend <- editGrob(get_legend(l3), vp = viewport(angle = 270))

grid.arrange(grobs = list(llegend, p, rlegend), ncol = 3, 
             widths = unit(c(3, 16, 3), "cm"))

- Martin Schmelzer

---

不用谢。我把它缩短了一点。对于图例图，您不需要使用facets等，因为我们只关心图例。还删除了您的数据代码。 - Martin Schmelzer

我认为这只对整体图例可行。因此，如果您想在左侧的图例中使用绿色和蓝色文本，则需要拆分图例。因此，您将有3个图例。然后，您需要排列图例1和图例2，之后再排列整体对象。你明白我的意思吗？ - Martin Schmelzer

更新了答案。 - Martin Schmelzer

请注意 cowplot::get_legend - Axeman

@Axeman 哦，不错。我不知道它在哪里实现了。我更新了答案。谢谢！ - Martin Schmelzer

Answer 2

这个源代码有一个简单易懂的答案。它描述了ggplot使用的逻辑，根据分配的aes映射创建图例，然后提供了一步一步的解决方案，没有所有这些额外的代码。非常适合具有第二个y轴的ggplot，即将多个geom_或stat_summary对象组合成一个漂亮流畅的图形的情况 :)

http://zevross.com/blog/2014/08/04/beautiful-plotting-in-r-a-ggplot2-cheatsheet-3/#manually-adding-legend-items-guides-override.aes

- Leah Carr