Using AUC for discrete predictor variables with inly two levels
doesn't seem very sensible. What are you planning to to with this
measure?
--
David.
On Jun 1, 2011, at 8:47 PM, <jin...@ga.gov.au> <jin...@ga.gov.au> wrote:
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...@ga.gov.au<mailto:jin...@ga.gov.au>
_______________________________________
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PLEASE do read the posting guide http://www.R-project.org/posting-guide.html
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David Winsemius, MD
West Hartford, CT
______________________________________________
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PLEASE do read the posting guide http://www.R-project.org/posting-guide.html
and provide commented, minimal, self-contained, reproducible code.
