从决策树函数JRip（RWeka库）访问单个结果

我正在使用库（RWeka）并在数据集上运行JRip函数。有人知道如何通过编程方式访问规则结果集，以便我可以单独访问每个规则吗

以下是仅用于说明目的的示例：

> library(datasets)
> head(npk)
block N P K yield
1     1 0 1 1  49.5
2     1 1 1 0  62.8
3     1 0 0 0  46.8
4     1 1 0 1  57.0
5     2 1 0 0  59.8
6     2 1 1 1  58.5
> tree_rip <- JRip(block ~ ., data = npk)
> tree_rip
JRIP rules:
===========

(yield <= 48.8) => block=4 (5.0/2.0)
(yield <= 52) => block=5 (4.0/1.0)
=> block=3 (15.0/11.0)

Number of Rules : 3

---

谢谢

这对我来说非常困难，因为我不是R与Java集成的用户。无论如何，在查看这些结果以了解REPL如何产生您所看到的结果后：

str(tree_rip)
# omitting about 15 lines of output
# - attr(*, "class")= chr [1:3] "JRip" "Weka_rules" "Weka_classifier"

getAnywhere(print.JRIP)
# no object named ‘print.JRIP’ was found
getAnywhere(print.Weka_rules)
# no object named ‘print.Weka_rules’ was found
help(pack="RWeka")
getAnywhere(print.Weka_classifier)
# this did succeed ... so I though `.jcall` should also succeed

.jcall(tree_rip$classifier, "S", "toString")
 #    Error: could not find function ".jcall"
 RWeka:::.jcall(tree_rip$classifier, "S", "toString")
 #    Error in get(name, envir = asNamespace(pkg), inherits = FALSE) : 
 #      object '.jcall' not found

。。。我发现需要加载pkg:rJava才能访问

.jcall函数

。显然，这是支持库未加载而仅附加的情况之一。（类似于[错误地]假设只有pkg:lattice加载时，

grid.text

才可用。）因此，这将为您提供所需的字符串集：

library(rJava)
as.matrix(scan(text=.jcall(tree_rip$classifier, "S", "toString") ,sep="\n", what="") )[
                                                                       -c(1:2, 6), ,drop=FALSE]
#------------
     [,1]                                  
[1,] "(yield <= 48.8) => block=4 (5.0/2.0)"
[2,] "(yield <= 52) => block=5 (4.0/1.0)"  
[3,] " => block=3 (15.0/11.0)" 

库（rJava）
as.matrix（扫描（text=.jcall（tree_rip$分类器，“S”，“toString”），sep=“\n”，what=“”）[
-c（1:2,6），drop=FALSE]
#------------
[,1]                                  
[1，]（屈服块=4（5.0/2.0）
[2，]（屈服块=5（4.0/1.0）
[3，]“=>block=3（15.0/11.0）”

str(tree_rip)
# omitting about 15 lines of output
# - attr(*, "class")= chr [1:3] "JRip" "Weka_rules" "Weka_classifier"

getAnywhere(print.JRIP)
# no object named ‘print.JRIP’ was found
getAnywhere(print.Weka_rules)
# no object named ‘print.Weka_rules’ was found
help(pack="RWeka")
getAnywhere(print.Weka_classifier)
# this did succeed ... so I though `.jcall` should also succeed

.jcall(tree_rip$classifier, "S", "toString")
 #    Error: could not find function ".jcall"
 RWeka:::.jcall(tree_rip$classifier, "S", "toString")
 #    Error in get(name, envir = asNamespace(pkg), inherits = FALSE) : 
 #      object '.jcall' not found

library(rJava)
as.matrix(scan(text=.jcall(tree_rip$classifier, "S", "toString") ,sep="\n", what="") )[
                                                                       -c(1:2, 6), ,drop=FALSE]
#------------
     [,1]                                  
[1,] "(yield <= 48.8) => block=4 (5.0/2.0)"
[2,] "(yield <= 52) => block=5 (4.0/1.0)"  
[3,] " => block=3 (15.0/11.0)"