问题描述
我想使用matlab工具箱进行特征选择.有一个很好的函数,称为sequencefs,可以很好地完成工作.但是,我无法将其与LibSVM函数集成以执行功能选择.它可以与KnnClassify一起正常工作,请有人帮我.这是KnnClassify的代码:
I want to use matlab toolbox to do feature selection. there is one good function there called sequentialfs that does a good job. However, I could not integrate it with LibSVM function to perform features selection. It works fine with KnnClassify, can somebody help me please. here is the code for KnnClassify:
fun1 = @(XT,yT,Xt,yt)...
fun1 = @(XT,yT,Xt,yt)...
(sum((yt ~= knnclassify(Xt,XT,yT,5))));
[fs,history] =顺序fs(fun1,data,label,'cv',c,'options',opts,'direction','forward');
[fs,history] = sequentialfs(fun1,data,label,'cv',c,'options',opts,'direction','forward');
推荐答案
您需要包装libsvm函数,以在特定功能集上训练和测试SVM.我建议在单独的.m文件中编写内容(尽管原则上我认为它可以在匿名函数中使用).像这样:
You'll need to wrap the libsvm functions to train and test an SVM on a particular featureset. I'd suggest writing things in a separate .m file (though in priciple I think it could go in an anonymous function). Something like:
function err = svmwrapper(xTrain, yTrain, xTest, yTest)
model = svmtrain(yTrain, xTrain, <svm parameters>);
err = sum(svmpredict(yTest, xTest, model) ~= yTest);
end
,然后您可以通过以下方式呼叫sequentialfs
:
and then you can call sequentialfs
with:
[fs history] = sequentialfs(@svmwrapper, ...);
(您可能需要检查svmtrain
的参数的顺序,我永远不记得它们应该是哪种方式).
(You may need to check the order of the arguments to svmtrain
, I can never remember which way round they should be).
想法是svmwrapper将训练SVM并在测试集上返回其错误.
The idea is that svmwrapper will train an SVM and return its error on the test set.
匿名等效项为:
svmwrapper = @(xTrain, yTrain, xTest, yTest)sum(svmpredict(yTest, xTest, svmtrain(yTrain, xTrain, <svm parameters>) ~= yTest);
看起来不太好.
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