Dimensionality reduction has been a standard methodology to deal with datasets that have a lot of features, more than a typical model can handle effectively. Reducing the number of features can also save time and storage space, while when it comes to sensitive data it can be a big plus as it enables anonymity in the people involved. What’s more, in some cases, a reduced dimensionality dataset can be more effective as there is less noise in it. However, conventional dimensionality reduction methods don’t always do the trick due to the inherent limitations they have. For example, PCA only considers linear relationships among the variables and a linear combination of features, as a solution.
Of course, other people are not sitting idle when it comes to this issue. There are several dimensionality reduction options that are being pursued, the most interesting of which is autoencoders. This AI-based method involves a data-driven approach to figuring out the nature of the data and creating new variables that can represent the underlying signal, by minimizing the error. The issue with this is that it often requires a lot of data and some specialized know-how in order to configure optimally. Also, this whole process may be fairly slow, due to the large number of computations involved.
An alternative approach has to do with feature fusion in a non-AI way. The idea is to maintain transparency to the extent this is possible, while at the same time optimize the whole process in terms of speed. The use of multiple operators, some linear and some non-linear, is essential, while the option of dropping useless features is also very useful. Naturally, this whole process would be more effective in the presence of a target variable, but it should be able to work without it, for better applicability. Whatever the case, the use of a metric able to handle non-linear correlations is paramount since the conventional correlation metric used leaves a lot to be desired.
Based on all this, it’s clear that the dimensionality reduction area is still capable of enhancements. Despite the great work that has been done already, there is still room for new methods that can address the limitations the existing methods have, which aren’t going away any time soon. Perhaps it would be best to explore this methodology of data engineering more, instead of focusing the latest and greatest system, which although intriguing, may sacrifice too much (e.g. transparency) in the name of accuracy, a trade-off that may no longer be cost-effective. Something to think about...
Zacharias Voulgaris, PhD
Passionate data scientist with a foxy approach to technology, particularly related to A.I.