Thank you Jim for your answer.Ok alpha( it is the speed of the boat) is a
range of number from 0.5 to 10 like 0.5,1,1.5,2...., I would like to have
the mean of x and y base on each value of alpha, because I have like ten
numbers of x for each value of speed, thats why I want the mean of that and
them i could create the roc plot with the new values.
I would say that alpha values are ordered already?

Thanks , Marta



2014-07-03 1:17 GMT+02:00 Jim Lemon <jim@bitwrit.com.au>:

> On Wed, 2 Jul 2014 02:42:31 PM Marta valdes lopez wrote:
> > Hello,
> >
> > I run this script , because i would like to do the mean of x and y base
> on
> > alpha as factor.
> >
> >
> > library(xlsx)
> > library(ROCR
> > filename<-"amanhecer roc.csv"
> > rocdata<- read.table(filename, sep=";",header=TRUE,dec=",")
> >
> > rocdata$alpha.15_12 <- as.factor(rocdata$alpha.15_12)
> >
> > TPaverage <- tapply(rocdata$y.15_12, rocdata$alpha.15_12, mean)
> > FPaverage <- tapply(rocdata$x.15_12, rocdata$alpha.15_12, mean)
> >
> > ###And them with the new data i want to create a plot, kind of ROC
> plot.
> >
> >  Anthias<-rocdata
> >  str(Anthias)
> > data(ROCR.simple)
> > pred <- prediction( ROCR.simple$predictions, ROCR.simple$labels )
> > perf <- performance( pred, "tpr", "fpr" )
> > windows(width = 9.5, height = 10.50)
> > par(mfrow = c(1,1))
> >
> > cc<-Anthias[1]
> > ee<-Anthias[2]
> > aa<-Anthias[3]
> > perf@x.name<-"FP"
> > perf@y.name<-"TP"
> > perf@alpha.name<-"Speed"
> > bb<-data.frame(aa)
> > perf@x.values<-bb
> > dd<-data.frame(cc)
> > perf@y.values<-dd
> > ff<-data.frame(ee)
> > perf@alpha.values<-ff
> >
> > plot(perf, main="Teste", colorize=TRUE,
> coloraxis.at=c(0,2,4,6,8,10),
> >  coloraxis.cex.axis=0.8, colorize.palette=(rainbow(256,start=0,
> end=0.7)),
> > lwd=7, colorkey.relwidth=0.4, yaxis.las=1)
> >
> > But after run the whole script i got the error:max not meaningful for
> > factors, anyone can help me?  I am a beginner in R ,so sorry if this is
> > wasting anyone's time*.*
> >
> Hi Marta,
> The error message is straightforward. Somewhere in one of the
> functions you have called, the "max" function is applied to your factor
> variable. The definition of factor variables is that the the actual values
> are of nominal class, in which there is no meaningful ordering of
> values, therefore the maximum value is undefined. You could try
> as.numeric(alpha), but that is dangerous as it depends on whether the
> sorting of values (default alphabetic) is what you want. If we knew what
> "alpha" was, it would help.
>
> Jim
>
>

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