Feature selection (FS) plays a key role in several scientific fields and in particular computational biology, making it possible to treat models with fewer variables, which in turn are easier to explain and might speed the experimental validation up, by providing valuable insight into the importance and their role. We propose a novel procedure for FS conceiving a two-steps approach. Firstly, a sparse coding based learning technique is used to find the best subset of features for each class of the train set. In doing so, it is assumed that a class is represented by using a subset of features, called representatives such that each sample, in a specific class, can be described as a linear combination of them. Secondly, the discovered feature subsets are fed to a class-specific feature selection scheme, to assess the effectiveness of the selected features in classification task. To this end, an ensemble of classifiers is built by training a classifier, one for each class on its own feature subset, i.e., the one discovered in the previous step and, a proper decision rule is adopted to compute the ensemble responses.

Feature selection has been widely used for eliminating redundant or irrelevant features and it can be done in two ways: Traditional Feature Selection (TFS) for all classes and Class-Specific Feature Selection (CSFS). CSFS is the process of finding different set of features for each class. In this kind of approach, different methods have been proposed. Conversely from a TFS algorithm, where a single feature subset is selected for discriminating among all the classes in a supervised classification problem, a CSFS algorithm selects a subset of feature for each class. A general framework for CSFS can use any traditional feature selector, for choosing a possible different subset for each class of a supervised classification problem. Depending on the type of the feature selector, the overall process may slightly change.

Sparse-Coding Based Approach for Class-Specific Feature Selection (SMBA-CSFS) is based on the concept of the Compressed Sensing. Basically, this approach is a joint sparse multiple optimization problem which tries to find a subset of features called representative, that best reconstruct/represent the entire dataset by linearly combining each retrieved feature component. We try to best represent each class-sample set of the train set by only using few representatives features.

1. Python 2.7 or greater
   
2. A CUDA version 5.0 or greater (facoltative). For installing, please refer to the official CUDA documention.

The software is written in Python. In order to correctly work, the software requires the following packages:

• numPy
• sciPy
• sklearn
• hdf5storage
• optional: pycuda
• optional: skcuda

NB: The SMBA class can eventually run faster by exploiting the CUDA environment. In case you cannot install (for some reason) the latter dependencies, you must manually remove the code which depends on these packages.

In order to use this algorithm, go into the project folder: /src and run the file CSFS_SMBA.py.

Comparison of several TFS accuracies against SMBA and SMBA-CSFS on nine data sets: (a) ALLAML(2), (b) LEUKEMIA(2), (c) CLL_SUB_111(3), (d) GLIOMA(4), (e) LUNG_C(5), (f) LUNG_D(7), (g) DLBCL(9), (h) CARCINOM(11), (i) GCM(14), when a varying number of features is selected. SVM classifier with 5-fold CV was used.

Comparison of several CSFS accuracies against SMBA-CSFS on nine data sets: (a) ALLAML(2), (b) LEUKEMIA(2), (c) CLL_SUB_111(3), (d) GLIOMA(4), (e) LUNG_C(5), (f) LUNG_D(7), (g) DLBCL(9), (h) CARCINOM(11), (i) GCM(14), when a varying number of features is selected. SVM classifier with 5-fold CV was used.

Davide Nardone, University of Naples Parthenope, Science and Techonlogies Departement, Msc Applied Computer Science https://www.linkedin.com/in/davide-nardone-127428102/

For any kind of problem, questions, ideas or suggestions, please don't esitate to contact me at:

• [email protected]

If you use the software in a scientific publication, please consider citing the following scientific manuscript:

@article{nardone2019,
author = {Nardone, Davide and Ciaramella, Angelo and Staiano, Antonino},
year = {2019},
month = {11},
pages = {25},
title = {A Sparse-Modeling Based Approach for Class Specific Feature Selection},
volume = {5},
journal = {PeerJ Computer Science},
doi = {10.7717/peerj-cs.237}
}