ggplot 一组直方图，直方图作为子图

Question

我在三个站点收集了数据，在每个站点中，这些数据针对多个受试者收集了多次。

数据如下所示：

set.seed(1)
df <- data.frame(site = c(rep("AA",1000),rep("BB",500),rep("CC",750)),
                 y = c(rnorm(1000,1,2),runif(500,1,3),rgamma(750,shape=1)))

#add subjects - using a function that randomly generates
#a number of subjects that adds up to their total at that site

site_a_subjects <- diff(c(0, sort(20*sample(19)), 1000))
site_b_subjects <- diff(c(0, sort(30*sample(9)), 500))
site_c_subjects <- diff(c(0, sort(40*sample(4)), 750))

#add these subjects
df$site_subjects <- c(unlist(sapply(1:20, function(x) rep(letters[x], site_a_subjects[x]))),
                  unlist(sapply(1:10, function(x) rep(letters[x], site_b_subjects[x]))),
                  unlist(sapply(1:5, function(x) rep(letters[x], site_c_subjects[x]))))

我想为每个站点绘制y 的直方图。 这条ggplot2 简单的线路很容易做到这一点：

ggplot(df, aes(x=y)) + geom_histogram(colour="black", fill="white") + facet_grid(. ~ site)

但是，我还想在每个站点直方图上绘制一个子图，它是该站点上每个主题观察次数的直方图。 比如添加：

hist(table(df$site_subjects[which(df$site == "AA")]))
hist(table(df$site_subjects[which(df$site == "BB")]))
hist(table(df$site_subjects[which(df$site == "CC")]))

分别到三个站点直方图。

知道怎么做吗？

我想知道是否可以调整 annotation_custom 来实现这一点？

此代码将起作用，但前提是：

ggplotGrob(ggplot(df, aes(x=site_subjects)) + geom_bar() + theme_bw(base_size=9))

command 可以接受 list 的 ggplot 对象或类似的东西。

这里是'几乎;解决方案： 首先弄清楚所有分面直方图中的最大条高度是多少

ymax <- max(sapply(unique(df$site), function(x) max(hist(df$y[which(df$site == x)],plot=FALSE)$counts)))

然后：

main.plot <- ggplot(df, aes(x=y)) + geom_histogram(colour="black", fill="gray") + facet_grid(~site) + scale_y_continuous(limits=c(0,1.2*ymax))
main.plot.info <- ggplot_build(main.plot)
xmin <- min(main.plot.info$data[[1]]$x[which(main.plot.info$data[[1]]$PANEL == 1)])
xmax <- max(main.plot.info$data[[1]]$x[which(main.plot.info$data[[1]]$PANEL == 1)])
main.plot <- main.plot + annotation_custom(grob = grid::roundrectGrob(),xmin = xmin, xmax = xmax, ymin=ymax, ymax=1.2*ymax)
sub.plot <- ggplotGrob(ggplot(df, aes(x=site_subjects)) + geom_bar() + theme_bw(base_size=9))
combined.plot <- main.plot +  annotation_custom(grob = sub.plot, xmin = xmin, xmax = xmax, ymin=ymax, ymax=1.2*ymax)

结果是：

Answer 1

执行此操作的一种方法是创建主图，然后通过在您想要插入图的每个位置创建视口来添加每个插图。我们使用来自grid 包的函数来执行这些操作。这是一个例子：

library(grid)

# Function to draw the inset plots 
  pp = function(var) {
    grid.draw(
      ggplotGrob(
        ggplot(df[df$site==var,], aes(site_subjects)) +
          geom_bar() +
          theme_bw(base_size=9)
      )
    )
  }  

# Function to place the viewports on the main graph
my_vp = function(x) {
  viewport(x=x, y=.8, width=0.25, height=0.2)
}

# Main plot
ggplot(df, aes(x=y)) + geom_histogram(colour="black", fill="white") + 
  facet_grid(. ~ site) +
  scale_y_continuous(limits=c(0,400))

# Draw each inset plot in a separate viewport
vp = my_vp(0.22)
pushViewport(vp)
pp("AA")
popViewport()

vp = my_vp(0.52)
pushViewport(vp)
pp("BB")
popViewport()

vp = my_vp(0.84)
pushViewport(vp)
pp("CC")

Answer 2

这是合理的：

ymax <- max(sapply(unique(df$site), function(x) max(hist(df$y[which(df$site == x)],plot=FALSE)$counts)))
sites <- unique(df$site)
plot.list <- sapply(sites, function(s) {
  main.plot = ggplot(df[which(df$site == s),], aes(x=y)) + geom_histogram(colour="black", fill="gray") + scale_y_continuous(limits=c(0,1.5*ymax))
  main.plot.info = ggplot_build(main.plot)
  xmin = min(main.plot.info$data[[1]]$x[which(main.plot.info$data[[1]]$PANEL == 1)])
  xmax = max(main.plot.info$data[[1]]$x[which(main.plot.info$data[[1]]$PANEL == 1)])
  sub.plot = ggplotGrob(ggplot(df[which(df$site == s),], aes(x=site_subjects)) + geom_bar() + theme_bw(base_size=9))
  return(ggplotGrob(main.plot + annotation_custom(grob = sub.plot, xmin = xmin, xmax = xmax, ymin=0.8*ymax, ymax=1.2*ymax)))})

grid.arrange(grobs=plot.list, ncol=3)