When I try to crate a grid of parameters for training with caret I get
various errors:
------------------------------------------------------------
> 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

The documentation for createGrid says:
------------------------------------------------------------
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'.


and gives the following examples:
------------------------------------------------------------
     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)


What I am doing wrong?

Also, what is the connection between len  above and tuneLength in the
argument for train?

Thanks,

James

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