r - 在 randomForest 包中忽略 nodesize 参数

Question

是否randomForest包忽略 nodesize范围？当我预测数据集的终端节点并检查计数时，我看到小于 nodesize 的值。 .我会自己提交一个修复程序，但底层代码是用 Fortran 编写的。如果有人可以确认此行为，我将联系包维护者并希望开始修复。

> library(randomForest)
> set.seed(1)
> rf <- randomForest(mtcars[,-1], mtcars[,1], nodesize = 5)
> nodes <- attr(predict(rf, mtcars[,-1], nodes = TRUE), 'nodes')

# node counts of first tree
> table(nodes[,1])

# first row is the terminal node ID#, second row is the count
 2  6  9 10 11 14 15 16 18 19 
 5  3  3  6  4  2  3  1  3  2 

添加系统信息:

Session info----------------------------------------------------------------
 setting  value                       
 version  R version 3.1.1 (2014-07-10)
 system   x86_64, mingw32             
 ui       RStudio (0.98.1049)         
 language (EN)                        
 collate  English_United States.1252  
 tz       America/Chicago             

Packages--------------------------------------------------------------------
 package      * version date       source        
 randomForest * 4.6.10  2014-07-17 CRAN (R 3.1.1)

Answer 1

包维护者的回应:

That parameter behaves as the way that Leo Breiman intended. The bug is in how the parameter was described. It’s the same as minsplit in the rpart:::rpart.control() function:

the minimum number of observations that must exist in a node in order for a split to be attempted.

下个版本我会把帮助文件里的描述改成
解决这个困惑。

最好的，安迪