在ggplot2中将空图添加到facet_wrap [英] adding empty graphs to facet_wrap in ggplot2

问题描述

我试图创建3个所有面板应该具有相同大小的图，所以我认为解决方案可能是facet_wrap。我的问题是，我不希望每个

  df < -  data.frame（group = c（1,1,2,2,2,3,3），
 name = c（'a'，'b'，'c'，'d'，'e'，'f'， 'g'），
x = c（1,2,3,4,5,6,7），
y = c（2,3,4,5,6,7,8））
 ggplot（df，aes（x，y））+ geom_point（）+ facet_wrap（〜name，ncol = 3）
  

结果将这些图形组合成一个连续的顺序，但我希望将它们分组到我的组列。

所以我期望的结果是

  ab _ 
cde 
fg _ 
  

但我得到的是

  abc 
def 
g __ 
  

有没有人建议像这样创建一个图表，也许通过添加空图表？我发现了另一个线程的评论和绘图，我创建了第二个解决方案。它使用 gridExtra 并直接操作ggplot grob。我认为它给出了期望的结果，但是以我介绍的形式，这是手动工作。此解决方案使用 facet_wrap 而不是 facet_grid 。

第一，我为变量 name 添加了一个占位符级别，这将确保创建空面并创建图形：

  df $ name2 < -  factor（df $ name，levels = c（'a'，'b'，''，'c'，'d' ，'e'，'f'，'g'，''））
p <-ggplot（df，aes（x，y））+ geom_point（）+ facet_wrap（〜name2，ncol = 3，drop = FALSE）
  

drop = FALSE 是什么导致 ggplot 绘制空的构面。
此图与我的第一个解决方案仅在标记方面有所不同。现在到棘手的部分：

  library（gridExtra）
g < -  ggplotGrob（p）
＃ ＃删除空面板
g $ grobs [％（c）中的名称（g $ grobs）％（panel3，panel9，strip_t3，strip_t9）]<  -  NULL 
 ## remove它们来自布局
g $ layout<  -  g $ layout [！（g $ layout $ name％in％c（panel-3，panel-9，
strip_t-3 ，strip_t-9）），] 
 ##将轴靠近面板
g $ layout [g $ layout $ name ==axis_b-9，c（t，b ）] = c（9,9）
  

基本上这就是评论所说的。如果您使用另一组图，请查看名称（g $ grobs）和 g $ layout $ name ，找出哪些元素必须被删除。

现在您可以使用

  grid.newpage（）
 grid.draw（g）
  

编辑2： $ b

对于较新版本的 ggplot2 ，上述解决方案不起作用。不幸的是，我不知道这个版本是从哪个版本开始的，但它在2.2.1版本中无法使用。

必须修改的部分是grob：

  g < -  ggplotGrob（p）
＃获取必须删除的grobs 
 rm_grobs <-g $ layout $ name％in％c（panel-1-3，panel-3-3，strip-t-3-1，strip-t-3-3 ）
＃remove grobs 
g $ grobs [rm_grobs]<  -  NULL 
g $ layout<  -  g $ layout [！rm_grobs，] 
 ##将轴移近面板
g $ layout [g $ layout $ name ==axis-b-3-3，c（t，b）] = c（14.5,14.5）
 grid.newpage（） 
 grid.draw（g）
  

主要变化是 g $ grobs 不再是已命名的列表，并且grobs的名称已更改。请注意，面板标记为panel-row-col，而灰色条则为strip-t-col-row。

I am trying to create 3 plots where all the panels should have the same size, so I thought the solution might be facet_wrap. My problem is, I do don't want the same number of graphs in each

df <- data.frame(group=c(1,1,2,2,2,3,3),
                 name=c('a','b','c','d','e','f','g'),
                 x=c(1,2,3,4,5,6,7),
                 y=c(2,3,4,5,6,7,8))
ggplot(df, aes(x,y)) + geom_point() + facet_wrap(~ name, ncol=3)

The result combines the graphs into a sequential order but I would like to group them by my group column.

So the result I expect is

a b _
c d e 
f g _

But what I get is

a b c
d e f
g _ _

Has anyone a suggestion to create a graph like this, maybe by adding empty graphs? I found a other thread Force facet_wrap to fill bottom row... But I couldn't get it to run in my case.

解决方案

facet_wrap simply puts one plot after the other and inserts "line breaks" after the appropriate number of plots. But there is also facet_grid that lets you specify a row and a column index. Your row index is group and I now add a column index as follows:

cols<-c(a=1,c=1,f=1,b=2,d=2,g=2,e=3)
df$col <- as.factor(cols[as.character(df$name)])

Now you can plot the facet grid with

ggplot(df, aes(x,y)) + geom_point() + facet_grid(group~col)

Of course, depending on what your problem is, you will have to think of an appropriate way to set the column indices.

This is the plot:

Edit:

In reaction to your comment and drawing from this answer, I created a second solution. It uses gridExtra and manipulates the ggplot grob directly. I think it gives the desired result, but in the form I present it, it is "manual work". This solution uses facet_wrap instead of facet_grid.

First, I add a "place holder levels" to the variable name, which will ensure that the empty facets are created and then create the plot:

df$name2 <- factor(df$name,levels=c('a','b','','c','d','e','f','g',' '))
p <- ggplot(df, aes(x,y)) + geom_point() + facet_wrap(~name2,ncol=3,drop=FALSE)

drop=FALSE is what causes ggplot to draw the empty facets. This plot differs from my first solution only in how the facets are labelled. Now to the tricky part:

library(gridExtra)
g <- ggplotGrob(p)
## remove empty panels
g$grobs[names(g$grobs) %in% c("panel3", "panel9", "strip_t3", "strip_t9")] <- NULL
## remove them from the layout
g$layout <- g$layout[!(g$layout$name %in% c("panel-3", "panel-9", 
                                           "strip_t-3", "strip_t-9")),]
## move axis closer to panel
g$layout[g$layout$name == "axis_b-9", c("t", "b")] = c(9,9)

This does basically what the comments say. If you work with another set of plots, look at the output of names(g$grobs) and g$layout$name to figure out, which elements have to be removed.

Now you can create the plot with

grid.newpage()
grid.draw(g)

Edit 2:

For newer versions of ggplot2 the above solution does not work. Unfortunately, I don't know with which version this started, but it definitely does not work with version 2.2.1.

The part that must be changed is the modification of the grob:

g <- ggplotGrob(p)
# get the grobs that must be removed
rm_grobs <- g$layout$name %in% c("panel-1-3", "panel-3-3", "strip-t-3-1", "strip-t-3-3")
# remove grobs
g$grobs[rm_grobs] <- NULL
g$layout <- g$layout[!rm_grobs, ]
## move axis closer to panel
g$layout[g$layout$name == "axis-b-3-3", c("t", "b")] = c(14.5, 14.5)
grid.newpage()
grid.draw(g)

The main changes are that g$grobs is no longer a named list and that the names of the grobs have changed. Note the panels are labelled as "panel-row-col" while for grey bars it is "strip-t-col-row".

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