相关向量机 相关向量机Relevance vector machineRVM是使用贝叶斯推理得到回归和分类的简约解的机器学习技术RVM的函数形式与支持向量机相同但是可以提供概率分类 其与带协方差函数的高斯过程等效 k  x  x     j   N  α j ϕ  x  x j  ϕ  x   x j  displaystyle kmathbf x mathbf x sum jNfrac alpha jphi mathbf x mathbf x jphi mathbf x mathbf x j 其中φ是核函数通常是高斯核函数xxN是训练集的输入向量來源請求 Compared to the SVM the Bayesian formulation allows avoiding the set of free parameters that the SVM has and that usually require crossvalidation based post optimizations However RVMs use an Expectation Maximization EMlike learning method and are therefore at risk of local minima unlike the standard SMObased algorithms employed by SVMs which are guaranteed to find a global optimum來源請求