[R] ROCR predictions

[Assa Yeroslaviz]

Hi everybody,

I am having a problem building a ROC curve with my data using the ROCR
package.

I have 10 lists of proteins such as attached (proteinlist.xls). each of the
lists was calculated with a different p-value.
The goal is to find the optimal p-value for the highest number of true
positives as well as lowaest number of false positives.

As far as I understood the explanations from the vignette of ROCR, my data
of TP and FP are the labels of the prediction function. But I don't know how
to assign the right predictions to these labels.

BTW, Is there a way of finding the optimum in the curve? I mean to find the
exact value in the ROC curve (see sheet 2 in the excel file for the ROC
curve).

I would like to thank for any help in advance

Assa