matlab求曲线的面积 AUROC

2022年4月22日 93次阅读 来源: zhanglei_edu

曲线面积的求法：

（1）任意曲线的面积求法：

>> x=0:pi/100:pi;
>> y=sin(x);
>> trapz(x,y)

ans =

    1.9998

（2）ROC曲线的面积求法：

function auc=auc(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=auc(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
    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]);
end

    原文作者：zhanglei_edu
    原文地址: https://blog.csdn.net/ZHONGHUNZHAIZHUREN/article/details/50503657
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