如何确定一个ggplot2对象的每个图层的几何类型？

问题描述

作为从我已经创建的情节中删除特定几何的努力的一部分（SO link ），我想动态地确定ggplot2对象每层的geom类型。

假设我不' t知道我添加图层的顺序，有没有办法动态查找具有特定几何图层的图层？如果我像下面一样打印图层，我可以看到图层存储在列表中，但我似乎无法访问geom类型。

<$ p $ （x = 1：3，y = 1：3，ymin = 0：2，ymax = 2：4）$ b（ggplot2）
dat $ bp p $ layers

[[1]]
映射：ymin = ymin，ymax = ymax
geom_ribbon：na.rm = FALSE，alpha = 0.3
stat_identity：
position_identity ：（width = NULL，height = NULL）

[[2]]
geom_line：
stat_identity：
position_identity：（width = NULL，height = NULL）


我不熟悉proto对象和我从proto尝试过的东西似乎不起作用（例如 p $ layers [[1]] $ str（））。

---

答案是w我能够想出一个动态移除图层的函数：

pre $ remove_geom< - function（ggplot2_object，geom_type） {
layers< - lapply（ggplot2_object $ layers，function（x）if（x $ geom $ objname == geom_type）NULL else x）
layers< - layers [！sapply（layers，is .nu​​ll）]

ggplot2_object $ layers< - layers
ggplot2_object
}

$ b $
如果你想要的是一个命名geom类型的字符串，你可以使用下面的代码：

  sapply（p $ layers，function（x）class（x $ geom）[1]）$ ​​b $ b  code> 

这会为每个图层的几何对象生成第一个类名称。在OP的例子中：



  [1]GeomRibbonGeomLine
  

上述答案中的代码不再给出2.2版本的结果。接受的答案产生两个NULL值，另一个答案产生完整的 ggproto 对象。

As part of an effort to remove a specific geom from a plot I've already created (SO link here), I'd like to dynamically determine the geom type of each layer of a ggplot2 object.

Assuming I don't know the order in which I added layers, is there a way to dynamically find layers with a specific geom? If I print out the layers like I do below I can see that the layers are stored in a list, but I can't seem to access the geom type.

library(ggplot2)
dat <- data.frame(x=1:3, y=1:3, ymin=0:2, ymax=2:4)
p <- ggplot(dat, aes(x=x, y=y)) + geom_ribbon(aes(ymin=ymin, ymax=ymax), alpha=0.3) + geom_line()
p$layers

[[1]]
mapping: ymin = ymin, ymax = ymax 
geom_ribbon: na.rm = FALSE, alpha = 0.3 
stat_identity:  
position_identity: (width = NULL, height = NULL)

[[2]]
geom_line:  
stat_identity:  
position_identity: (width = NULL, height = NULL)

I'm not familiar with proto objects and things I've tried from the proto documentation don't seem to work (e.g. p$layers[[1]]$str()).

---

Thanks to the answers below I was able to come up with a function that removes a layer dynamically:

remove_geom <- function(ggplot2_object, geom_type) {
  layers <- lapply(ggplot2_object$layers, function(x) if(x$geom$objname == geom_type) NULL else x)
  layers <- layers[!sapply(layers, is.null)]

  ggplot2_object$layers <- layers
  ggplot2_object
}

解决方案

ggplot 2.2 update:If what you want is a character string naming the geom type, you can use:

sapply(p$layers, function(x) class(x$geom)[1])

which yields the first class name for the geom object of each layer. In the OP's example:

[1] "GeomRibbon" "GeomLine" 

The code in the answers above no longer give the results shown for version 2.2 The accepted answer yields two NULL values, and the other answer yields full ggproto objects.

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