Re: [R] calculating AUCs for each of the 1000 boot strap samples

2011-03-18 Thread taby gathoni
Brian, Thanks for the insights, i did manage to play around with the sample sizes and I have got some better results with both ROCR and pROC Thanks also to Andrija for providing the main code and insights. Thanks alot Taby --- On Thu, 3/17/11, Brian Diggs dig...@ohsu.edu wrote:

Re: [R] calculating AUCs for each of the 1000 boot strap samples

2011-03-17 Thread Brian Diggs
Taby, First, it is better to reply to the whole list (which I have included on this reply); there is a better chance of someone helping you. Just because I could help with one aspect does not mean I necessarily can (or have the time to) help with more. Further comments are inline below.

Re: [R] calculating AUCs for each of the 1000 boot strap samples

2011-03-17 Thread Frank Harrell
Taby, At the end of your note are you referring to the bootstrap confidence intervals in the external validation case, i.e., not corrrected for overfitting? If so you can get that without the bootstrap (e.g., Hmisc package rcorr.cens function). You can get bootstrap overfitting-corrected ROC

[R] calculating AUCs for each of the 1000 boot strap samples

2011-03-16 Thread taby gathoni
Hallo, I modified a code given by Andrija, a contributor in the list  to achieve two objectives: create 1000 samples from a list of 207 samples with each of the samples cointaining 20 good and 20 bad. THis i have achievedcalcuate AUC each of the 1000 samples, this i get an error. Please see

Re: [R] calculating AUCs for each of the 1000 boot strap samples

2011-03-16 Thread Brian Diggs
On 3/16/2011 8:04 AM, taby gathoni wrote: data-data.frame(id=1:(165+42),main_samp$SCORE, x=rep(c(BAD,GOOD),c(42,165))) f-function(x) { + str.sample-list() + for (i in 1:length(levels(x$x))) + { + str.sample[[i]]-x[x$x==levels(x$x)[i] ,][sample(tapply(x$x,x$x,length)[i],20,rep=T),] + } +