Support vector machines (SVM) is another one of those mysterious black box methods in machine learning. This post will try to explain in simple terms what SVM are and their strengths and weaknesses.
SVM is a combination of nearest neighbor and linear regression. For the nearest neighbor, SVM uses the traits of an identified example to classify an unidentified one. For regression, a line is drawn that divides the various groups.It is preferred that the line is straight but this is not always the case
This combination of using the nearest neighbor along with the development of a line leads to the development of a hyperplane. The hyperplane is drawn in a place that creates the greatest amount of distance among the various groups identified.
The examples in each group that are closest to the hyperplane are the support vectors. They support the vectors by providing the boundaries for the various groups.
If for whatever reason a line cannot be straight because the boundaries are not nice and night. R will still draw a straight line but make accommodations through the use of a slack variable, which allow for error and or for examples to be in the wrong group.
Another trick used in SVM analysis is the kernel trick. A kernel will add a new dimension or feature to the analysis by combining features that were measured in the data. For example, latitude and lonigitude might be combine mathematically to make altitude. This new feature is now used to develop the hyperplane for the data.
There are several different types of kernel tricks that achieve their goal using various mathematics. There is no rule for which one to use and playing different choices is the only strategy currently.
Pros and Cons
The pros of SVM is their flexibility of use as they can be used to predict numbers or classify. SVM are also able to deal with nosy data and are easier to use than artificial neural networks. Lastly, SVM are often able to resist overfitting and are usually highly accurate.
Cons of SVM include they are still complex as they are a member of black box machine learning methods even if they are simpler than artificial neural networks. The lack of a criteria over kernel selection makes it difficult to determine which model is the best.
SVM provide yet another approach to analyzing data in a machine learning context. Success with this approach depends on determining specifically what the goals of a project are.