Hi all,
I used the following code and data to get auc values for two sets of predictions:
            library(caret)
> table(predicted1, trainy)
   trainy
    hard soft
  1   27    0
  2   11   99
> aucRoc(roc(predicted1, trainy))
[1] 0.5


> table(predicted2, trainy)
   trainy
    hard soft
  1   27    2
  2   11   97
> aucRoc(roc(predicted2, trainy))
[1] 0.8451621

predicted1:
1 1 2 2 2 1 2 1 1 2 2 2 2 2 2 2 2 2 2 2 2 2 1 2 2 2 2 2 2 2 2 2 1 2 2 2 2 2 1 2 2 2 2 1 1 2 2 2 2 2 1 2 2 2 2 2 1 2 2 2 2 2 2 2 2 2 2 2 2 2 2 1 2 2 2 2 2 2 2 1 2 2 2 2 2 1 1 1 2 2 1 1 1 2 2 2 2 2 1 1 2 2 2 2 2 2 1 1 1 1 1 2 2 2 2 2 2 2 2 2 2 2 2 2 2 2 2 2 2 2 2 2 2 2 2 2 2

predicted2:
1 1 2 1 2 1 2 1 1 2 2 2 2 2 2 2 2 2 2 2 2 2 1 2 2 2 2 2 2 2 2 1 1 2 2 2 2 2 1 2 2 2 2 1 1 2 2 2 2 2 1 2 2 2 2 2 1 2 2 2 2 2 2 2 2 2 2 2 2 2 2 1 2 2 2 2 2 2 2 1 2 2 2 2 2 1 1 1 2 2 1 1 1 2 2 2 2 2 1 1 2 2 2 2 2 2 1 1 1 1 1 2 2 2 2 2 2 2 2 2 2 2 2 2 2 2 2 2 2 2 2 2 2 2 2 2 2

trainy:
hard hard hard soft soft hard hard hard hard soft soft soft soft soft soft hard soft soft soft soft soft soft hard soft soft soft soft soft soft soft soft soft hard soft soft soft soft soft hard soft soft soft soft hard hard soft soft soft hard soft hard soft soft soft soft soft hard soft soft soft soft soft soft soft soft hard soft soft soft soft soft hard soft soft soft soft soft soft soft hard soft soft soft hard hard hard hard hard soft soft hard hard hard soft hard soft soft soft hard hard soft soft soft soft soft hard hard hard hard hard hard hard soft soft soft soft soft soft soft soft soft soft soft soft soft soft soft soft hard soft soft soft soft soft soft soft soft
Levels: hard soft

> Sys.info()
                     sysname                      release                      version                     nodename
                   "Windows"                      "XP"        "build 2600, Service Pack 3"        "PC-60772"
                     machine
                       "x86"

I would expect predicted1 is more accurate that the predicted2. But the auc values show an opposite. I was wondering whether this is a bug or I have done something wrong.  Thanks for your help in advance!

Cheers,

Jin
____________________________________
Jin Li, PhD
Spatial Modeller/Computational Statistician
Marine & Coastal Environment
Geoscience Australia
GPO Box 378, Canberra, ACT 2601, Australia

Ph: 61 (02) 6249 9899; email: jin.li@ga.gov.au<mailto:jin.li@ga.gov.au>
_______________________________________



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