R help - Oct 2009 - need help explain the routine input parameters for seROC and cROC found in the R archive

Please help.

I found the code in the archive.

The author of this script says: "The first function (seROC) calculate
the standard error of ROC curve, the second function (cROC) compare
ROC curves."


Can some one explain to me what are the na, nn and r parameters which
are used as the input to the following two functions?

Thanks much in advance.
> From: Bernardo Rangel Tura
> Date: Thu 16 Dec 2004 - 07:30:37 EST
>
> seROC<-function(AUC,na,nn){
> a<-AUC
> q1<-a/(2-a)
> q2<-(2*a^2)/(1+a)
> se<-sqrt((a*(1-a)+(na-1)*(q1-a^2)+(nn-1)*(q2-a^2))/(nn*na))
> se
> }
>
> cROC<-function(AUC1,na1,nn1,AUC2,na2,nn2,r){
> se1<-seROC(AUC1,na1,nn1)
> se2<-seROC(AUC2,na2,nn2)
>
> sed<-sqrt(se1^2+se2^2-2*r*se1*se2)
> zad<-(AUC1-AUC2)/sed
> p<-dnorm(zad)
> a<-list(zad,p)
> a
> }
>
-- 
Waverley @ Palo Alto

waverley palo wrote:
> 
> I found the code in the archive.
> 
> The author of this script says: "The first function (seROC) calculate
> the standard error of ROC curve, the second function (cROC) compare
> ROC curves."
> 
> 
>> From: Bernardo Rangel Tura
> ...
> 
The original post has given the definition of the parameters; see

http://markmail.org/message/zqjeadvflv2fkumd

But also check Frank Harrell's comment on using (nor better: not using)
these standard errors.

http://markmail.org/message/sy5nlkdl2rk4roxm


Dieter



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