ROC curve for a binary classifier in MATLAB

Question

I have a binary classifier, which classifies an input X as class zero if its predicted value is below some threshold (say T), and one otherwise.
I have all predicted and actual values for every input. So I can have both predicted class and actual class of an input.

Now I want to have the ROC curve for this classifier with MATLAB. How should I do it?

Answer 1

Use perfcurve:

[X,Y] = perfcurve(labels,scores,posclass);
plot(X,Y);

labels are the true labels of the data, scores are the output scores from your classifier (before the threshold) and posclass is the positive class in your labels.