# SVM (Support Vector Machine) A Training Algorithm for Optimal Margin Classifiers(1992) [[paper link]](http://www.svms.org/training/BOGV92.pdf) Phoebe Huang Pytorch Tainan 2019/7/20 --- ## Task Discription ![f1](https://i.imgur.com/xFD1kLB.png) Find decision function $D(\mathbb{x})$, ![f2](https://i.imgur.com/Juq9Ln1.png) ---- SVM Main Idea: Maximum Margin ${M}$ ![fig1](https://i.imgur.com/kbKG2NA.png =600x) ---- The decision functions $D(\mathbb{x})$ must be linear in their parameters but are not restricted to linear dependences of $\mathbb{x}$. ![f3](https://i.imgur.com/Crhbj9T.png) ---- In the dual space the decision functions are of the form ![f4](https://i.imgur.com/b6N0rM7.png) The function $K$ is a predefined kernel ![f5](https://i.imgur.com/hQhV6sD.png) ---- Provided that the expansion stated in equation 5 exists, equations 3 and 4 are **dual representations** of the same decision function and ![f6](https://i.imgur.com/BVuCBiG.png) First, the margin between the class boundary and the training patterns is formulated in the **direct space**. This problem description is then transformed into the **dual space** by means of the **Lagrangian**. --- ## In the Direct Space In the direct space, ![f7](https://i.imgur.com/sdCcUAa.png) ![fig1](https://i.imgur.com/kbKG2NA.png =300x) ---- The distance between this hyperplane and pattern $\mathbb{x}$ is $\frac{ D(\mathbb{x})}{||\mathbb{w}||}$. All data satisfying ![f8](https://i.imgur.com/ITpq8er.png) ---- The objective of the training algorithm is to find $\mathbb{w}$ that maximum $M$ ![f9](https://i.imgur.com/exLR1ju.png) <!-- ?? --> The bound $M^{*}$ is attained for those patterns satisfying ![f10](https://i.imgur.com/Zp25RYx.png) ---- ![f11](https://i.imgur.com/kIAi2X3.png) ![f12](https://i.imgur.com/u9yHFrX.png) ---- ![f13](https://i.imgur.com/eXXQ7Hr.png) --- ## In the Dual Space ![f14](https://i.imgur.com/pnkjdEn.png) ---- ![f15](https://i.imgur.com/6dFqvHL.png) ![f16](https://i.imgur.com/CDy1QvS.png) ---- ![f17](https://i.imgur.com/OR8QL3I.png) ![f17.5](https://i.imgur.com/8giSfKb.png) ---- ![f18](https://i.imgur.com/zGKAKXg.png) ![f19](https://i.imgur.com/fXMPpKK.png) --- # 3 Properties of this Algorithm ## 3.1 Properties of the solution ![f20](https://i.imgur.com/jcPActS.png) ![f21](https://i.imgur.com/eHk0T3c.png)
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