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?

Solution

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.

Comments

[Matin Kh]

What do X and Y represent?

[lennon310]

@MatinKh X is false positive rate, Y is true positive rate by default. You can change them as well. Check this page: mathworks.com/help/stats/perfcurve.html

[Ran]

@MatinKh X and Y are the values for the axis of the ROC plot.

[TariqS]

@Ran You have mentioned that scores are output scores from classifier before applying threshold. Then how do we apply threshold