Brief Introduction to Some of Chemometric Methods Used in SAR

2 Brief Introduction to Some of Chemometric Methods Used in SAR 

Now a series of chemometric methods have been used in SAR. Generally speaking, different chemometric methods are suitable for different cases for each kind of these methods has its own advantages and disadvantages, and the best approach should be the combination of several chemometric techniques that complement each other, as that we have discussed in chapter one. So it is helpful to introduce briefly the different chemometric methods widely used in SAR. Here chemical pattern recognition methods will be specially emphasized since different projections can provide plentiful information from different projection maps from the hyperspaces. In SAR practice, some chemical pattern recognition methods are often used as complementary methods in the application of SVM. 

Starting from the pioneering work of Kowalskii published in the year of 1972, various chemical pattern recognition techniques have been the powerful tools in SAR work. 

In SAR, chemical pattern recognition methods can be categorized into unsupervised methods and supervised pattern recognition methods. 

The unsupervised pattern recognition normally consists of cluster analysis. Using a couple of dozen descriptors of molecules, it is possible to see which activities of molecules are most similar and draw a picture of these similarities, called a dendrogram, in which more closely related activities are closer to each other 

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