[R] plotting several ROC curves on the same graph

[meytar]

Hello 
I am trying to make a graph of 10 different lines built each from 4
different 
segments and to add a darker line that will represent the average of all
graphs 
- all in the same plot.Actually each line is a ROC plot 
The code I'm using for plotting one line is as follows: 

logit.roc.plot <- function(r, title="ROC curve") { 
old.par <- par(no.readonly = TRUE); on.exit(par(old.par)) 
par(xaxs="i", yaxs="i") 
plot(1 - r$spec, r$sens, xlim=c(0, 1), ylim=c(0,1), type="l", 
xlab="(1 - specificity): false positive rate", 
ylab="sensitivity: true positive rate", 
col="grey82", lwd=2); 
points(1 - r$spec, r$sens,pch=20, cex=1.5, col="grey82") 
abline(0, 1, lty=2); 
segments(1-r$spec, 1-r$spec, 1-r$spec, r$sens, lty=3) 
#text(1 - max(r$spec,na.rm=T), 
r$sens[which.max(r$spec)],r$pts[which.max(r$spec)],pos=2,cex=0.8) 
text(0, 0.9, paste("Area under ROC:",round(logit.roc.area(r),4)), pos=4) 
title(main = title) 
} 
r[5,]=c(0,0,1,10) 
logit.roc.plot(r) 
r=r[-5,] 
text(1 - max(r$spec,na.rm=T), 
r$sens[which.max(r$spec)],r$pts[which.max(r$spec)],pos=2,cex=0.8) 

while r is  a MATRIX (4x4) with 
colnames=c("pts",sens","spec",iterationnumber.") 
and I have for each ROC curve a different matrix but all matrices have the
same 
size. (They are organized as a list of 10 matrices by the size 4X4 each) 

Would appreciate your help in putting all ROC curves on the same plot. 
Thank you 

-- 
Meytar

--
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