[R] Extracting slots from ROCR prediction objects

From: Stacey Burrows <stacey.burrows_at_yahoo.ca>
Date: Thu, 22 May 2008 14:08:59 -0400 (EDT)


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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