Discovering feature relevancy and dependency by kernel-guided probabilistic model-building evolution.
BACKGROUND
Discovering relevant features (biomarkers) that discriminate etiologies of a disease is useful to provide biomedical researchers with candidate targets for further laboratory experimentation while saving costs; dependencies among biomarkers may suggest additional valuable information, for example, to characterize complex epistatic relationships from genetic data. The use of classifiers to guide the search for biomarkers (the so-calledwrapperapproach) has been widely studied. However, simultaneously searching for relevancy and dependencies among markers is a less explored ground.


RESULTS
We propose a new wrapper method that builds upon the discrimination power of a weighted kernel classifier to guide the search for a probabilistic model of simultaneous marginal and interacting effects. The feasibility of the method was evaluated in three empirical studies. The first one assessed its ability to discover complex epistatic effects on a large-scale testbed of generated human genetic problems; the method succeeded in 4 out of 5 of these problems while providing more accurate and expressive results than a baseline technique that also considers dependencies. The second study evaluated the performance of the method in benchmark classification tasks; in average the prediction accuracy was comparable to two other baseline techniques whilst finding smaller subsets of relevant features. The last study was aimed at discovering relevancy/dependency in a hepatitis dataset; in this regard, evidence recently reported in medical literature corroborated our findings. As a byproduct, the method was implemented and made freely available as a toolbox of software components deployed within an existing visual data-mining workbench.


CONCLUSIONS
The mining advantages exhibited by the method come at the expense of a higher computational complexity, posing interesting algorithmic challenges regarding its applicability to large-scale datasets. Extending the probabilistic assumptions of the method to continuous distributions and higher-degree interactions is also appealing. As a final remark, we advocate broadening the use of visual graphical software tools as they enable biodata researchers to focus on experiment design, visualisation and data analysis rather than on refining their scripting programming skills.
Universidad Distrital FJC, School of Engineering, Bogota, Colombia.
Nestor
N
Rodriguez
Universidad Distrital FJC, School of Engineering, Bogota, Colombia.
Sergio
S
Rojas-Galeano
Dependency estimation; Epistasis; Feature selection; Hepatitis dataset; Relevancy discovery; Visual programming tools