Revision: 19728
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at October 29, 2009 15:12 by benjamin
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function auc=areaundercurve(FPR,TPR); % given true positive rate and false positive rate calculates the area under the curve % true positive are on the y-axis and false positives on the x-axis % sum rectangular area between all points % example: auc=areaundercurve(FPR,TPR); [x2,inds]=sort(FPR); x2=[x2,1]; % the trick is in inventing a last point 1,1 y2=TPR(inds); y2=[y2,1]; xdiff=diff(x2); xdiff=[x2(1),xdiff]; auc1=sum(y2.*xdiff); % upper point area auc2=sum([0,y2([1:end-1])].*xdiff); % lower point area auc=mean([auc1,auc2]);
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http://www.myoutsourcedbrain.com/2008/11/receiver-operating-characteristic-roc.html
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My implementation corresponding to Tom Fawcett's algorithm 3 in "roc graphs: notes and practical considerations for researchers, " 2004. Please see blog post for explanations and leave comments there.
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area under the curve (AUC)
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MatLab