[R] (no subject)

[Liaw, Andy]

> -----Original Message-----
> From: NICOLAS DEIG
> 
> hello,
> 
> i am encoutering problems with a function of R concerning the
> classification trees. 
> 
> In the library {tree}, when I use the function "tree" to grow a
         ^^^^^^^

That should be "package"...

> classification tree it should give me an object of class 
> "tree". Then I
> should be allowed to use this "tree" object in the function "cv.tree"
> that  requires an object of class "tree" in order to run a
> cross-validation experiment. 
> There is the problem, when I do this the following message appears:
> "Error in as.data.frame.default(data) : can't coerce function into a
> data.frame". 
> So instead of considering the object as an  object of class tree the
> function "cv.tree" handles it like a data.frame.
> 
> Does anyone knows why or how to work on a class "tree" object so that
> "cv.tree" can handle it?

Please show how you did it the the error you got.  I can't reproduce the
problem you described:

> library(tree)
> iris.tree <- tree(Species ~ ., iris)
> iris.cvtree <- cv.tree(iris.tree)
> iris.cvtree
$size
[1] 6 5 4 3 2 1

$dev
[1]  52.33779  45.94317  46.28027  63.43450 151.84608 335.57375

$k
[1]       -Inf   4.228650   4.717398  15.957916  95.676543 190.954250

$method
[1] "deviance"

attr(,"class")
[1] "prune"         "tree.sequence"

Andy


 
> Thanks in advance...
> Nicolas Deig
> 
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