Hi Stacey,

ROCR uses S4 classes. The elements are accessed using "@" instead of "$".
You can find an example on slide 12 of the following slide deck:
http://rocr.bioinf.mpi-sb.mpg.de/ROCR_Talk_Tobias_Sing.ppt

Also have a look at the R code that appears when you type "demo(ROCR)" in R
which contains some more examples related to your question.

Hope that helps,
  Tobias


On Thu, May 22, 2008 at 8:32 PM, Jorge Ivan Velez <jorgeivanvelez@gmail.com>
wrote:

> Hi Stacey,
> Try this:
>
> library(ROCR)
> data(ROCR.simple)
> pred <- prediction(ROCR.simple$predictions,ROCR.simple$labels)
> perf <- performance(pred,"sens","spec")
> cuts <- unlist(slot(perf,"alpha.values"))
> cuts
>
> HTH,
>
> Jorge
>
>
> On Thu, May 22, 2008 at 2:08 PM, Stacey Burrows <stacey.burrows@yahoo.ca>
> wrote:
>
> > Hi,
> >
> > I have an object from the prediction function from the ROCR package and I
> > would like to extract one of the slots from the object, for example the
> > cutoffs slot. However the usual techniques ($, [["name"]]) of subsetting
> > don't work. How can I assess the lists in the slots?
> >
> > Here is an example of what I am working with:
> >
> > library(ROCR)
> > data(ROCR.simple)
> > pred <- prediction(ROCR.simple$predictions,ROCR.simple$labels)
> >
> > > str(pred)
> > Formal class 'prediction' [package "ROCR"] with 11 slots
> >  ..@ predictions:List of 1
> >  .. ..$ : num [1:200] 0.613 0.364 0.432 0.140 0.385 ...
> >  ..@ labels     :List of 1
> >  .. ..$ : Ord.factor w/ 2 levels "0"<"1": 2 2 1 1 1 2 2 2 2 1 ...
> >  ..@ cutoffs    :List of 1
> >  .. ..$ : num [1:201]   Inf 0.991 0.985 0.985 0.983 ...
> >  ..@ fp         :List of 1
> >  .. ..$ : num [1:201] 0 0 0 0 1 1 2 3 3 3 ...
> >  ..@ tp         :List of 1
> >  .. ..$ : num [1:201] 0 1 2 3 3 4 4 4 5 6 ...
> >  ..@ tn         :List of 1
> >  .. ..$ : num [1:201] 107 107 107 107 106 106 105 104 104 104 ...
> >  ..@ fn         :List of 1
> >  .. ..$ : num [1:201] 93 92 91 90 90 89 89 89 88 87 ...
> >  ..@ n.pos      :List of 1
> >  .. ..$ : int 93
> >  ..@ n.neg      :List of 1
> >  .. ..$ : int 107
> >  ..@ n.pos.pred :List of 1
> >  .. ..$ : num [1:201] 0 1 2 3 4 5 6 7 8 9 ...
> >  ..@ n.neg.pred :List of 1
> >  .. ..$ : num [1:201] 200 199 198 197 196 195 194 193 192 191 ...
> > >
> >
> > Thanks in advance,
> > Stacey
> >
> >
> > ---------------------------------
> >
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> >
> > ______________________________________________
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> > http://www.R-project.org/posting-guide.html
> > and provide commented, minimal, self-contained, reproducible code.
> >
>
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>
> ______________________________________________
> R-help@r-project.org mailing list
> https://stat.ethz.ch/mailman/listinfo/r-help
> PLEASE do read the posting guide
> http://www.R-project.org/posting-guide.html
> and provide commented, minimal, self-contained, reproducible code.
>

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