[R] how to operate a S4 objecti

[David Winsemius]

On Feb 3, 2010, at 12:25 PM, Hongbin Zhang wrote:

> I have a R object which has a value (see below, e.g., the  
> "0.8341875") I like to extract to put into a simple form, e.g., an  
> array.
>
> how could I do that?
>
> below is the code:
>
>> library(ROCR)
>> data(ROCR.simple)
>> pred <- prediction( ROCR.simple$predictions, ROCR.simple$labels)
>> auc <- performance(pred,"auc")
>> auc

 > arr <- array(, dim=c(3,3,3) )
 > arr[1,1,1] <- auc at y.values[[1]]
 > arr
, , 1

           [,1] [,2] [,3]
[1,] 0.8341875   NA   NA
[2,]        NA   NA   NA
[3,]        NA   NA   NA

, , 2

      [,1] [,2] [,3]
[1,]   NA   NA   NA
[2,]   NA   NA   NA
[3,]   NA   NA   NA

, , 3

      [,1] [,2] [,3]
[1,]   NA   NA   NA
[2,]   NA   NA   NA
[3,]   NA   NA   NA


>
> An object of class performance
>
> [1] "None"
>
> Slot "y.name":
> [1] "Area under the ROC curve"
>
> Slot "alpha.name":
> [1] "none"
>
> Slot "x.values":
> list()
>
> Slot "y.values":
> [[1]]
> [1] 0.8341875
>
>
> Slot "alpha.values":
> list()
>
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> and provide commented, minimal, self-contained, reproducible code.

David Winsemius, MD
Heritage Laboratories
West Hartford, CT