如何使用 grid.arrange 排列任意数量的 ggplot？

Question

这是交叉发布在 ggplot2 google group

我的情况是，我处理输出任意值的函数绘图数量（取决于输入数据由用户提供）。该函数返回 n 个图的列表，我想将这些图以 2 x 2 的形式排列。我正在努力解决以下同时发生的问题：

1. 如何才能灵活地处理任意（n）数量的地块？
2. 我怎样才能指定我希望它们布局为 2 x 2

我当前的策略使用 gridExtra 包中的 grid.arrange 。它可能不是最佳的，特别是因为，这是关键，它完全不起作用。这是我的注释示例代码，尝试了三个图：

library(ggplot2)
library(gridExtra)

x <- qplot(mpg, disp, data = mtcars)
y <- qplot(hp, wt, data = mtcars)
z <- qplot(qsec, wt, data = mtcars)

# A normal, plain-jane call to grid.arrange is fine for displaying all my plots
grid.arrange(x, y, z)

# But, for my purposes, I need a 2 x 2 layout. So the command below works acceptably.
grid.arrange(x, y, z, nrow = 2, ncol = 2)

# The problem is that the function I'm developing outputs a LIST of an arbitrary
# number plots, and I'd like to be able to plot every plot in the list on a 2 x 2
# laid-out page. I can at least plot a list of plots by constructing a do.call()
# expression, below. (Note: it totally even surprises me that this do.call expression
# DOES work. I'm astounded.)
plot.list <- list(x, y, z)
do.call(grid.arrange, plot.list)

# But now I need 2 x 2 pages. No problem, right? Since do.call() is taking a list of
# arguments, I'll just add my grid.layout arguments to the list. Since grid.arrange is
# supposed to pass layout arguments along to grid.layout anyway, this should work.
args.list <- c(plot.list, "nrow = 2", "ncol = 2")

# Except that the line below is going to fail, producing an "input must be grobs!"
# error
do.call(grid.arrange, args.list)

正如我习惯做的那样，我谦虚地挤在角落里，热切地等待比我聪明得多的社区的明智反馈。特别是如果我让这件事变得比需要的更难的话是。

Answer 1

你就快到了！问题是 do.call 期望您的参数位于命名的 list 对象中。您已将它们放入列表中，但作为字符串，而不是命名列表项。

我认为这应该可行：

args.list <- c(plot.list, 2,2)
names(args.list) <- c("x", "y", "z", "nrow", "ncol")

正如本和约书亚在评论中指出的那样，我可以在创建列表时指定名称：

args.list <- c(plot.list,list(nrow=2,ncol=2))

或

args.list <- list(x=x, y=y, z=x, nrow=2, ncol=2)

Answer 2

试试这个，

require(ggplot2)
require(gridExtra)
plots <- lapply(1:11, function(.x) qplot(1:10,rnorm(10), main=paste("plot",.x)))

params <- list(nrow=2, ncol=2)

n <- with(params, nrow*ncol)
## add one page if division is not complete
pages <- length(plots) %/% n + as.logical(length(plots) %% n)

groups <- split(seq_along(plots), 
  gl(pages, n, length(plots)))

pl <-
  lapply(names(groups), function(g)
         {
           do.call(arrangeGrob, c(plots[groups[[g]]], params, 
                                  list(main=paste("page", g, "of", pages))))
         })

class(pl) <- c("arrangelist", "ggplot", class(pl))
print.arrangelist = function(x, ...) lapply(x, function(.x) {
  if(dev.interactive()) dev.new() else grid.newpage()
   grid.draw(.x)
   }, ...)

## interactive use; open new devices
pl

## non-interactive use, multipage pdf
ggsave("multipage.pdf", pl)

Answer 3

我回答得有点晚了，但在 R Graphics Cookbook 上偶然发现了一个解决方案，该解决方案使用名为 multiplot 的自定义函数执行非常类似的操作。也许它会帮助其他发现这个问题的人。我还添加了答案，因为该解决方案可能比该问题的其他答案更新。

一页上的多个图表 (ggplot2)

这是当前的函数请使用上面的链接，因为作者指出它已更新为 ggplot2 0.9.3，这表明它可能会再次更改。

# Multiple plot function
#
# ggplot objects can be passed in ..., or to plotlist (as a list of ggplot objects)
# - cols:   Number of columns in layout
# - layout: A matrix specifying the layout. If present, 'cols' is ignored.
#
# If the layout is something like matrix(c(1,2,3,3), nrow=2, byrow=TRUE),
# then plot 1 will go in the upper left, 2 will go in the upper right, and
# 3 will go all the way across the bottom.
#
multiplot <- function(..., plotlist=NULL, file, cols=1, layout=NULL) {
  require(grid)

  # Make a list from the ... arguments and plotlist
  plots <- c(list(...), plotlist)

  numPlots = length(plots)

  # If layout is NULL, then use 'cols' to determine layout
  if (is.null(layout)) {
    # Make the panel
    # ncol: Number of columns of plots
    # nrow: Number of rows needed, calculated from # of cols
    layout <- matrix(seq(1, cols * ceiling(numPlots/cols)),
                    ncol = cols, nrow = ceiling(numPlots/cols))
  }

 if (numPlots==1) {
    print(plots[[1]])

  } else {
    # Set up the page
    grid.newpage()
    pushViewport(viewport(layout = grid.layout(nrow(layout), ncol(layout))))

    # Make each plot, in the correct location
    for (i in 1:numPlots) {
      # Get the i,j matrix positions of the regions that contain this subplot
      matchidx <- as.data.frame(which(layout == i, arr.ind = TRUE))

      print(plots[[i]], vp = viewport(layout.pos.row = matchidx$row,
                                      layout.pos.col = matchidx$col))
    }
  }
}

创建绘图对象：

p1 <- ggplot(...)
p2 <- ggplot(...)
# etc.

然后将它们传递给 multiplot：

multiplot(p1, p2, ..., cols = n)