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，应该用于绘制ROC曲线。您能否帮我理解如何从perfcurve函数的数据中获取输入？

感谢您的回复！

Answer 1

我制作了一个小脚本，显示了给定两列矩阵输入的perfcurve的基础知识。如果你在MATLAB中执行它并仔细查看它，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.

输入ROC曲线

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