ROC 曲线的输入

Question

我有一个 2 列矩阵，其中每一行是健康（第 1 列）和不健康（2 列）患者的观察结果。另外，我有 5 个分区值应该用于绘制 ROC 曲线。 您能否帮助我了解如何从这些数据中获取 perfcurve 函数的输入？

感谢您的回复！

Answer 1

我制作了一个小脚本，显示给定两列矩阵输入的性能曲线的基础知识。如果您在 MATLAB 中执行此操作并仔细查看，那么使用 perfcurve 应该没有问题

%Simulate your data as Gaussian data with 1000 measurements in each group. 
%Lets give them a mean difference of 1 and a standard deviation of 1.
Data = zeros(1000,2);
Data(:,1) = normrnd(0,1,1000,1);
Data(:,2) = normrnd(1,1,1000,1);

%Now the data is reshaped to a vector (required for perfcurve) and  I create the labels.
Data = reshape(Data,2000,1);
Labels = zeros(size(Data,1),1);
Labels(end/2+1:end) = 1; 
%Your bottom half of the data (initially second column) is now group 1, the
%top half is group 0. 
%Lets set the positive class to group 1.
PosClass = 1;

%Now we have all required variables to call perfcurve. We will give
%perfcurve the 'Xvals' input to define the values at which the ROC curve is
%calculated. This parameter can be left out to let matlab calculate the
%curve at all values. 
[X Y] = perfcurve(Labels,Data,PosClass, 'Xvals', 0:0.25:1);

%Lets plot this
plot(X,Y)

%One limitation in scripting it like this is that you must have equal group
%sizes for healthy and sick. If you reshape your Data matrix to a vector
%and keep a seperate labels vector then you can also handle groups of
%different sizes.