Analysis A Unifying Framework

More specifically, input data analysis methods are similar to input-output methods, but rely on different strategies for extracting the relevant information. With reference to the general expression in Eq. (4), the resulting analyzed or latent variable for all input methods can be represented as 

Sometimes more meaningful features may be obtained by considering the behavior of both input and output variables together in the analysis. 

Typically, input-output analysis methods extract the most relevant signal features by relating the analyzed variables to process output variables, y,-, 

Specific data analysis methods can be derived from Eqs. (5) and (6) depending on decisions about the input transformation, type of activation or basis functions, and optimization criteria. These decisions form the basis of a common framework for comparing all empirical modeling methods (Bakshi and Utojo, 1999). 

Based on the nature of input transformation, both input and input-output analysis methods can be classified into the following three categories  

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