R help - Mar 2008 - ROC analysis

Hello list,

I am trying to perform ROC analysis and count the AUC in order to validate
my results. I use package ROCR. I would like to count the AUC not under the
cutoff found by "performance" but to use another cutoff that I
calculate.
How could I change the following  command in order to get what I want?
perform=performance(pred,measure="auc",x.measure="cutoff"),
where pred is a
prediction object.

Thank you very much,
Eleni

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Eleni

Does the fpr.stop argument do what you want? This is described in 
?performance under the details of the "auc" measure. Try, e.g.

perform=performance(pred,measure="auc",fpr.stop=0.5)


Richard.


Eleni Christodoulou wrote:
> Hello list,
>
> I am trying to perform ROC analysis and count the AUC in order to validate
> my results. I use package ROCR. I would like to count the AUC not under the
> cutoff found by "performance" but to use another cutoff that I
calculate.
> How could I change the following  command in order to get what I want?
>
perform=performance(pred,measure="auc",x.measure="cutoff"),
where pred is a
> prediction object.
>
> Thank you very much,
> Eleni
>
> 	[[alternative HTML version deleted]]
>
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