[R] listing components of an object

[Charilaos Skiadas]

On Mar 2, 2008, at 4:12 PM, Nair, Murlidharan T wrote:

> Is there a method to list the components of an object, instead of  
> looking at the help for that method?  Let me be more clear with an  
> example
>
> data(iris)
>   ## tune `svm' for classification with RBF-kernel (default in svm),
>   ## using one split for training/validation set
>
>   obj <- tune(svm, Species~., data = iris,
>               ranges = list(gamma = 2^(-1:1), cost = 2^(2:4)),
>               tunecontrol = tune.control(sampling = "fix")
>              )
>
>   ## alternatively:
>   ## obj <- tune.svm(Species~., data = iris, gamma = 2^(-1:1), cost  
> = 2^(2:4))
>
>   summary(obj)
>   plot(obj)
> ---------------------------------
> For tune, an object of class tune, including the components:
>
> best.parameters a 1 x k data frame, k number of parameters.
> best.performance best achieved performance.
> performances if requested, a data frame of all parameter  
> combinations along with the corresponding performance results.
> train.ind list of index vectors used for splits into training and  
> validation sets.
> best.model if requested, the model trained on the complete training  
> data using the best parameter combination.
>
> I got the above by doing ?tune.
>
> Is there a function that helps be do this?

Usually str(obj), or possibly as.list(obj) for many objects, will  
give you the sort of information that I think you want, but what's  
wrong with ?tune ? In other words, why do you want this list?  
Typically, it is advisable that one uses methods to access the  
components of an object, like for instance "coef(obj)" for the  
coefficients in a model object. This is so that the internal  
representation of an object can change without breaking your code,  
and a host of other reasons.

> Thanks ../Murli

Haris Skiadas
Department of Mathematics and Computer Science
Hanover College