J48树(RWeka)中的属性及其值 [英] Properties and their values out of J48 tree (RWeka)

问题描述

如果运行以下命令:

library(RWeka) 
data(iris) 
res = J48(Species ~., data = iris)

res将是从Weka_tree继承的类J48的列表.如果您打印

res will be a list of class J48 inheriting from Weka_tree. If you print it

R> res
J48 pruned tree
------------------

Petal.Width <= 0.6: setosa (50.0)
Petal.Width > 0.6
|   Petal.Width <= 1.7
|   |   Petal.Length <= 4.9: versicolor (48.0/1.0)
|   |   Petal.Length > 4.9
|   |   |   Petal.Width <= 1.5: virginica (3.0)
|   |   |   Petal.Width > 1.5: versicolor (3.0/1.0)
|   Petal.Width > 1.7: virginica (46.0/1.0)

Number of Leaves  :     5

Size of the tree :  9

我想按从右到左的顺序获取属性及其值.因此，在这种情况下:

I would like to get the properties and their values by their order from right to left. So for this case:

Petal.Width, Petal.Width, Petal.Length, Petal.Length.

我试图将res输入一个因子并运行命令:

I tried to enter res to a factor and to run the command:

str_extract(paste0(x, collapse=""), perl("(?<=\\|)[A-Za-z]+(?=\\|)"))

没有成功. 只是要记住，我们应该忽略左边的字符.

with no success. Just to remember that we should ignore the left around characters.

推荐答案

一种方法是将RWeka的J48对象转换为partykit的party对象.您只需要按as.party(res)即可，这将为您完成所有解析，并返回一个更易于与标准化提取器功能等配合使用的结构.

One way to do this is to convert the J48 object from RWeka to a party object from partykit. You just need to as as.party(res) and this does all the parsing for you and returns a structure that is easier to work with with standardized extractor functions etc.

特别地，您可以使用在其他讨论中给出的关于ctree对象等的所有建议.请参见

In particular you can then use all advice given in other discussions about ctree objects etc. See

• 确定参与方中所有不同的变量ctree nodel

  而且我认为以下内容至少应满足您的要求:

  And I think the following should do at least part of what you want:

  library("partykit")
  pres <- as.party(res)
  partykit:::.list.rules.party(pres)
  ##                                                                                  2 
  ##                                                               "Petal.Width <= 0.6" 
  ##                                                                                  5 
  ##                     "Petal.Width > 0.6 & Petal.Width <= 1.7 & Petal.Length <= 4.9" 
  ##                                                                                  7 
  ## "Petal.Width > 0.6 & Petal.Width <= 1.7 & Petal.Length > 4.9 & Petal.Width <= 1.5" 
  ##                                                                                  8 
  ##  "Petal.Width > 0.6 & Petal.Width <= 1.7 & Petal.Length > 4.9 & Petal.Width > 1.5" 
  ##                                                                                  9 
  ##                                            "Petal.Width > 0.6 & Petal.Width > 1.7" 
  

  更新:操作人员将我与名单外的联系人联系在一起，询问相关问题，要求提供树的特定印刷表示形式.我将我的解决方案包括在这里，以防它对其他人有用.

  Update: The OP contacted me off-list for a related question, asking for a specific printed representation of the tree. I'm including my solution here in case it is useful for someone else.

  他想用()符号表示层次结构级别以及拆分变量的名称.一种方法是(1)提取基础数据的变量名:

  He wanted to have ( ) symbols signalling the hierarchy levels plus the names of the splitting variables. One way to do so would be to (1) extract variable names of the underlying data:

  nam <- names(pres$data)
  

  (2)将树的递归节点结构转换为平面列表(这对于构造所需的字符串有些方便):

  (2) Turn the recursive node structure of the tree into a flat list (which is somewhat more convenient for constructing the desired string):

  tr <- as.list(pres$node)
  

  (3a)初始化字符串:

  (3a) Initialize the string:

  str <- "("
  

  (3b)递归在字符串中添加方括号和/或变量名:

  (3b) Recursively add brackets and/or variable names to the string:

  update_str <- function(x) {
     if(is.null(x$kids)) {
       str <<- paste(str, ")")
     } else {
       str <<- paste(str, nam[x$split$varid], "(")
       for(i in x$kids) update_str(tr[[i]])
     }
  }
  

  (3c)从根节点开始调用递归:

  (3c) Call the recursion, starting from the root node:

  update_str(tr[[1]])
  str
  ## [1] "( Petal.Width ( ) Petal.Width ( Petal.Length ( ) Petal.Width ( ) ) )"
  

  这篇关于J48树(RWeka)中的属性及其值的文章就介绍到这了，希望我们推荐的答案对大家有所帮助，也希望大家多多支持IT屋！