使用网格对齐ggplot2轴

Question

我有一个ggplot2线图奇数个面。我想在空白处添加一个x值边缘分布的箱形图。 boxplot应该是水平的，并与其他facet共享一个共同的x轴。由于默认Boxplot几何是垂直的，因此需要coord_flip()。正因为如此，我不认为有可能将boxplot数据与其他facet包含在同一个df中，并使用虚拟因子变量进行分面。

使用grid，我可以识别空的视口并插入boxplot，但我想让x轴排队。对类似问题的解答（请参阅here或here）建议在ggExtra包中使用align_plots，但我不认为这将与分面工作。我在下面包含了一个简单的可重复使用的示例如果我得到这个工作，我还必须编辑空面板Grob来创建一个匹配其他方面的新标签。任何建议，将不胜感激。

library(ggplot2) 
#generate df for faceted line graphs 
df <- data.frame(x = rep(1:100, times=7), 
     facet_var = as.factor(rep(1:7, each=100)), 
     y = runif(7*100) 
    ) 
#create faceted line graphs 
p <- ggplot(data = df, aes(x, y)) + 
    geom_line() + facet_wrap(~ facet_var, ncol=2) 

#generate df for boxplot 
xdata <- runif(1000, min = 0, max = 100) 
boxdf <- data.frame(x=xdata, group=rep(1,length(xdata))) 

#create boxplot removing axes and margins 
q <- ggplot(data = boxdf, aes(as.factor(group),x)) + geom_boxplot() + 
     coord_flip() + labs(x=NULL) + 
     opts(axis.text.x = theme_blank(), axis.title.x=theme_blank(), 
     axis.text.y = theme_blank(), axis.title.y=theme_blank(), 
     axis.ticks = theme_segment(colour = "white"), 
     panel.margin = 0, plot.margin = unit(rep(0,4), "lines") 
     ) 

print(p) 
downViewport("panel-14-5") 
print(q, newpage=F) 

编辑： kohske的有用的答案后，我试着去适应不同的X限制和休息的代码。这里是代码的x限制和中断的范围（0,80）。可能我在代码中缺少一些需要用限制来修改的东西。

library(ggplot2) 
df <- data.frame(x = rep(1:80, times=7), 
     facet_var = as.factor(rep(1:7, each=80)), 
     y = runif(7*80) 
    ) 

# label for marginal plot 
df <- rbind(df, data.frame(x = NA, y = NA, facet_var = "Boxplot wow")) 

p <- ggplot(data = df, aes(x, y)) + 
    geom_line() + facet_wrap(~ facet_var, ncol=2) + 
    # set limits for adjustment 
    coord_cartesian(xlim = c(0, 80)) + 
    #scale_x_continuous(breaks = 1:4*20) 
    opts() 

xdata <- runif(1000, min = 0, max = 80) 
boxdf <- data.frame(x=xdata, group=rep(1,length(xdata))) 

q <- ggplot(data = boxdf, aes(as.factor(group),x)) + geom_boxplot() + 

    # set breaks and limits for adjustment 
    coord_flip(ylim = c(0, 80)) + labs(x=NULL) + 
    scale_y_continuous(breaks = 1:4*20) + 

    # opts for full region drawing: 
    # see https://kohske.wordpress.com/2010/12/25/drawing-on-full-region-in-ggplot2/ 
    opts(
    legend.position = "none", 
    panel.margin = unit(0,"null"), 
    plot.margin = rep(unit(0,"null"),4), 
    axis.ticks = theme_blank(), 
    axis.text.x = theme_blank(), 
    axis.text.y = theme_blank(), 
    axis.title.x = theme_blank(), 
    axis.title.y = theme_blank(), 
    axis.ticks.length = unit(0,"null"), 
    axis.ticks.margin = unit(0,"null") 
) 

print(p) 

# remove unused panel 
grid.remove("panel-14-5") 

downViewport("panel-14-5") 
print(q, newpage=F) 

Answer 1

这里是一个略微肮脏的黑客：

library(ggplot2) 
df <- data.frame(x = rep(1:100, times=7), 
     facet_var = as.factor(rep(1:7, each=100)), 
     y = runif(7*100) 
    ) 

# label for marginal plot 
df <- rbind(df, data.frame(x = NA, y = NA, facet_var = "Boxplot wow")) 

p <- ggplot(data = df, aes(x, y)) + 
    geom_line() + facet_wrap(~ facet_var, ncol=2) + 
    # set limits for adjustment 
    coord_cartesian(xlim = c(0, 100)) 

xdata <- runif(1000, min = 20, max = 80) 
boxdf <- data.frame(x=xdata, group=rep(1,length(xdata))) 

q <- ggplot(data = boxdf, aes(as.factor(group),x)) + geom_boxplot() + 

    # set breaks and limits for adjustment 
    coord_flip(ylim = c(0, 100)) + labs(x=NULL) + 
    scale_y_continuous(breaks = 1:5*20) + 

    # opts for full region drawing: 
    # see https://kohske.wordpress.com/2010/12/25/drawing-on-full-region-in-ggplot2/ 
    opts(
    legend.position = "none", 
    panel.margin = unit(0,"null"), 
    plot.margin = rep(unit(0,"null"),4), 
    axis.ticks = theme_blank(), 
    axis.text.x = theme_blank(), 
    axis.text.y = theme_blank(), 
    axis.title.x = theme_blank(), 
    axis.title.y = theme_blank(), 
    axis.ticks.length = unit(0,"null"), 
    axis.ticks.margin = unit(0,"null") 
) 

print(p) 

# remove unused panel 
grid.remove("panel-14-5") 

downViewport("panel-14-5") 
print(q, newpage=F)