在ggplot2中添加第二个x轴

Question

在"图形"包中,可以向直方图添加第二个x轴(表示分布的百分位数),如下所示:

x  <- rnorm(1000)
hist(x, main="", xlab="Bias")
perc  <- quantile(x, seq(from=.00, to=1, by=.1))
axis(1,at=perc,labels=c("0","10%","20%","30%","40%","50%","60%","70%","80%","90%","100%"),cex=0.5, pos= -90)

当然,这看起来很尴尬.那么我怎么能修改下面的ggplot2代码来添加第二个x轴,甩掉百分位数,而第一个x轴应该指示原始值？:

library(ggplot2)
theme_classic(base_size = 12, base_family = "")
x  <- rnorm(1000)
qplot(x, main="", xlab="Bias")
perc  <- quantile(x, seq(from=.00, to=1, by=.1))

有帮助吗？提前谢谢了!

Answer 1

我不完全确定你所追求的是什么,因为你的第一个例子并没有真正产生你描述的东西.

但就简单地沿x轴添加百分比和原始值而言,最简单的策略可能是简单地将两者与一组标签中的换行符结合起来:

dat <- data.frame(x = rnorm(1000))
perc <- quantile(dat$x,seq(from = 0,to = 1,by = 0.1))
l <- paste(round(perc,1),names(perc),sep = "\n")
> ggplot(dat,aes(x = x)) + 
     geom_histogram() + 
     scale_x_continuous(breaks = perc,labels = l)

Answer 2

这是另一种方法,它使用annotate(...)并且不要求两个标度具有相同的中断.

library(ggplot2)
library(grid)

set.seed(123)
x     <- rnorm(1000)
perc  <- quantile(x, seq(from=.00, to=1, by=.1))
labs  <- gsub("\\%","",names(perc))   # strip "%" from names
yval  <- hist(x,breaks=30,plot=F)$count
yrng  <- diff(range(yval))
g1 <- ggplot() +
  geom_histogram(aes(x=x))+ 
  xlim(range(x))+
  coord_cartesian(ylim=c(0,1.1*max(yval)))+
  labs(x="")+
  annotate(geom = "text", x = perc, y = -0.1*yrng, label = labs, size=4) +
  annotate(geom = "text", x=0, y=-0.16*yrng, label="Bias", size=4.5)+
  theme(plot.margin = unit(c(1, 1, 2, 1), "lines"))

g2 <- ggplot_gtable(ggplot_build(g1))
g2$layout$clip[g2$layout$name == "panel"] <- "off"
grid.draw(g2)

这会添加第二个x轴和标签annotate(...).最后三行代码关闭了视口的剪切.否则注释不可见.

感谢@Henrik对这个问题的回答.