使用插入符号时用于 rf (randomForest) 的 createGrid 出错

Question

当我尝试使用caret 为训练创建一个参数网格时，我遇到了各种错误：

> my_grid <- createGrid("rf")
Error in if (p <= len) { : argument is of length zero

> my_grid <- createGrid("rf", 4)
Error in if (p <= len) { : argument is of length zero

> my_grid <- createGrid("rf", len=4)                                        
Error in if (p <= len) { : argument is of length zero

createGrid 的文档说：

This function creates a data frame that contains a grid of
     complexity parameters specific methods.
Usage:
       createGrid(method, len = 3, data = NULL)
Arguments:
  method: a string specifying which classification model to use. See
          'train' for a full list.
     len: an integer specifying the number of points on the grid for
          each tuning parameter.
    data: the training data (only needed in the case where the 'method'
          is 'cforest', 'earth', 'bagEarth', 'fda', 'bagFDA', 'rpart',
          'svmRadial', 'pam', 'lars2', 'rf' or 'pls'). The outcome
          should be in a column called '.outcome'.

并给出以下正确工作的例子：

 createGrid("rda", 4)
 createGrid("lm")
 createGrid("nnet")
 
 ## data needed for SVM with RBF:
 ## Not run:
 
 tmp <- iris
 names(tmp)[5] <- ".outcome"
 head(tmp)
 createGrid("svmRadial", data = tmp, len = 4)
 ## End(Not run)

有了这个，我做错了什么？

后续问题：

len 作为createGrid 的自变量和train 的自变量中的tuneLength 之间有什么联系？ len 和tuneLength 可以一起使用吗？他们是什么关系？

其他有用的话题：

如果有帮助，这里有一个线程描述了如何在caret 中使用createGrid 和train：caret::train: specify model-generation-parameters

Answer 1

您从示例中提取的代码对我来说很好（并注意它解决了您在 Rhelp 上发布时存在的问题）：

tmp <- iris
 names(tmp)[5] <- ".outcome"
 head(tmp)
 createGrid("svmRadial", data = tmp, len = 4)
#-------
     .sigma   .C
1 0.7500934 0.25
2 0.7500934 0.50
3 0.7500934 1.00
4 0.7500934 2.00

编辑：

>  createGrid("rf", data = tmp, len = 4)
randomForest 4.6-7
Type rfNews() to see new features/changes/bug fixes.

Attaching package: ‘randomForest’

The following object(s) are masked from ‘package:Hmisc’:

    combine

note: only 3 unique complexity parameters in default grid. Truncating the grid to 3 .

  .mtry
1     2
2     3
3     4

我再说一遍：还有什么问题？