绘图的两个方面的两个单独的y轴标题，同时使用ggplot2保留方面顶部的标签

Question

我有这个数据框：

> str(DF)
'data.frame':   14084 obs. of  6 variables:
.
.
.
 $ Variables: chr  "Height" "Height" "Height" "Height" ...
 $ Values   : num  245 129 301 162 123 125 115 47 46 135 ...
 $ Year     : Factor w/ 2 levels "2015","2016": 1 1 1 1 1 1 1 1 1 1 ...

我使用facet_wrap()自由轴刻度将图分成两个小平面（分为两列）。

ggplot(data = DF, aes(x = Year, y = Values)) +
  geom_boxplot() +
  facet_wrap("Variables", scales = "free")

我的问题是：
两个构面共享一个共同的y轴标题。但是，我想为两个方面提供两个单独的y轴标题。常见的x轴标题对我来说很好。

我碰到了这个问题， 使用带有facet_wrap的ggplot2显示不同的轴标签， 但是它并不能解决我想要的问题，因为我不想失去顶部的切面标签。而且，我的构面是水平排列的。

我尝试使用labs()：

. . . +
labs(y=c("A", "B"))

但这只是将第一个构面的y轴标题更改为A，而第二个构面则保持不变。

我该如何解决这个问题？

任何帮助，将不胜感激。

Answer 1

不知道我是否完全了解您的需求，但这是我根据您建议的链接和此链接进行的尝试。

library(ggplot2)
library(grid)
library(gtable)

# Some fake data
set.seed(2018)
df <- data.frame(variables = rep(c("var1", "var2"), times = 100),
                 values = rnorm(100),
                 year = as.factor(2001:2010))

# Make a plot with positioning the strip labels to the right of each facet,
# acting as OY axis titles.
# We will add the top strip labels in the next step,
# using the `grid` & `gtable` packages functionality.
p <- ggplot(df, aes(x = year, y = values, group = year) ) +
  geom_boxplot() +
  facet_wrap(~ variables, scales = "free_y", nrow = 1, 
             strip.position = "left", 
             labeller = as_labeller(c(var1 = "Example var1", 
                                      var2 = "Example var2") ) )  +
  ylab(NULL) +
  theme(strip.background = element_blank(),
        strip.placement = "outside",
        # Customize theme so that is black & white style as requested
        panel.background = element_rect(fill = NA, colour = 'black'),
        panel.grid = element_blank())
p

使用grid＆gtable软件包的功能添加顶部标签条：

# Get gtable object
g <- ggplotGrob(p)
# Sometimes helpful to get an idea about the grobs' position
grid.show.layout(gtable:::gtable_layout(g)) 

# Add an extra top row (make some space)
g <- gtable_add_rows(x = g, heights = unit(0.65, 'cm'), pos = 2)
# First strip
g <- gtable_add_grob(x = g,
                     grobs = list(rectGrob(gp = gpar(col = NA, 
                                                     fill = NA)),
                                  textGrob(label = "var1", 
                                           gp = gpar(col = "black"))),
                     t = 3, l = 7, b = 3, r = 7, 
                     name = c("strip-top-1-rectg", "strip-top-1-text"))
# Second strip
g <- gtable_add_grob(x = g,
                     grobs = list(rectGrob(gp = gpar(col = NA, 
                                                     fill = NA)),
                                  textGrob(label = "var2", 
                                           gp = gpar(col = "black"))),
                     t = 3, l = 13, b = 3, r = 13, 
                     name = c("strip-top-2-rectg", "strip-top-2-text")) 

# Draw the edited plot
grid.newpage()
grid.draw(g)