ROC曲线的输入

Question

我有一个2列矩阵，其中每行是健康（第1列）和非健康（2列）患者的观察结果。此外，我有5个分区值应该用来绘制ROC曲线。 你能否帮我理解如何从perfcurve函数获取这些数据的输入？

谢谢你的回复！

Answer 1

我已经制作了一个小脚本，显示给定两列矩阵输入的perfcurve的基础知识。如果你在MATLAB中执行此操作并仔细观察它，那么使用perfcurve

%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.