Matlab libsvm-如何找到w系数 [英] Matlab libsvm - how to find the w coefficients

问题描述

如何找到向量w，即与分离平面垂直的向量?

How can find what the vector w is, i.e. the perpendicular to the separation plane?

推荐答案

这就是我的操作方式对偶格式.

This is how I did it here. If I remember correctly, this is based on how the dual form of the SVM optimisation works out.

model = svmtrain(...);
w = (model.sv_coef' * full(model.SVs));

偏见是(而且我真的不记得为什么它是负面的):

And the bias is (and I don't really remember why its negative):

bias = -model.rho;

然后对具有N个实例和M个特征的N个M个数据集特征"进行分类(对于线性SVM)

Then to do the classification (for a linear SVM), for a N-by-M dataset 'features' with N instances and M features,

predictions = sign(features * w' + bias);

如果内核不是线性的，那么这将无法为您提供正确的答案.

If the kernel is not linear, then this won't give you the right answer.

有关更多信息，请参见如何生成线性SVM的原始变量w? ，来自libsvm的手册.

For more information see How could I generate the primal variable w of linear SVM? , from the manual of libsvm.

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