在聚会/partykit树中向终端条形图添加水平线 [英] Add horizontal line to terminal barplots in party / partykit trees

问题描述

我正在使用partykit中的ctree函数.

I am using the ctree function from partykit.

library(rpart)
library(partykit)

fit <- ctree(Kyphosis ~ Age + Number + Start, data=kyphosis)
plot(fit, terminal_panel=node_barplot)

我想在每个条形图中添加一条额外的水平线，以指示整个数据集的平均响应，即此处为0.79.

I want to add an additional horizonal line to each barplot, indicating the average reponse across the dataset, i.e. at 0.79 here.

prop.table(table(kyphosis$Kyphosis))

    absent   present 
 0.7901235 0.2098765

方法:我开始修改传递给terminal_panel参数的node_barplot函数.但是源代码很长，几乎没有注释.因此，我尝试逐步进行操作，将功能分解为前两行代码(外加一个额外的打印命令).但是，如果我运行它，则对象y是NULL并引发错误.

Approach: I started to modify the node_barplot function that is passed to the terminal_panel argument. But the source code is very long and comes with almost no comments. So I tried to go step by step, stripping down the function to its first two lines of code (plus an extra print command). However, if I run it, the object y is NULL and an error is thrown.

node_barplot2 <- function(obj, ...)
{   
  y <- obj$fitted[["(response)"]]   # first lime from node_barplot source
  print(y)
  stopifnot(is.factor(y) || isTRUE(all.equal(round(y), y)) || is.data.frame(y))
}

plot(fit, terminal_panel=node_barplot2)

> Error in round(y) : Non-numeric argument in mathematical function

作为其原始代码，我不太了解这里哪里出错了和如何绘制水平线.有什么想法吗?

As its the original code, I do not quite see where I go wrong here and how I could draw the horizontal line. Any ideas?

推荐答案

partykit区分面板"功能和面板生成"功能:

The partykit distinguishes "panel" functions and "panel-generating" functions:

• 前者只希望将树的node作为其唯一参数，然后绘制该节点(使用grid图形).

• The former just expect the node of a tree as their sole argument and then draw this node (using grid graphics).

后者希望将一棵完整的树作为其第一个参数，以及用于自定义的其他参数.它们返回一个面板"函数(仅带有参数node)，其中某些信息(如x和y范围)存储在函数环境中.

The latter expect a full tree as their first argument plus further arguments for customization. They return a "panel" function (with only argument node) where certain informations like the x and y ranges are stored in the function environment.

要发出一个函数是一个面板生成函数的信号，它必须具有类"grapcon_generator".因此

To signal that a function is a panel-generating function, it has to have class "grapcon_generator". Hence

class(node_barplot)
## [1] "grapcon_generator"

要向函数中添加某些图形元素，建议复制整个node_barplot源代码(包括末尾的类分配)，然后添加所需的元素，例如，可以使用的水平参考线grid.lines().

To add certain graphical elements to the function, I would recommend copying the whole node_barplot source code (including the class assignment at the end) and then add the elements you need, e.g., a horizontal reference line you can draw with grid.lines().

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