This code implements the simulation results reported in:

M. W. Spratling (2014) Classification using sparse representations: a biologically plausible approach, Biological Cybernetics, 108(1):61-73.

Please cite this paper if this code is used in, or to motivate, any publications.

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USAGE

This code was tested with MATLAB Version 7.10 (R2010a).

To use this software:

    run matlab 
    cd to the directory containing this code 

Some functions make use of the nansuite toolbox by Jan Glaescher, available at http://www.mathworks.com/matlabcentral/fileexchange/6837. These functions should thus be installed somewhere on your matlab path.

To perform an experiment to test the classification performance of a sparse solver run the following command:

  >> test_sparse_classifier;

The output of the test_sparse_classifier code is a list of 6 numbers. These numbers provide the follow information:

1. The percentage of exemplars misclassified when classification is performed by assigning the signal to the class of the dictionary element with the MAXimum coefficient,

2. The percentage of exemplars misclassified when classification is performed by assigning the signal to the class of the dictionary elements with the highest SUM of coefficients,

3. The percentage of exemplars misclassified when classification is performed by assigning the signal to the class of the dictionary elements which generate the smallest reconstruction error

4. The total execution time (in seconds)

5. The Hoyer sparsity of the coefficients, averaged over all the signals that were classified

6. The NSE between the signal and the reconstruction of the signal produced by the sparse representation, averaged over all the signals that were classified

The set-up of the experiment is controlled by the parameters in the function global_parameters.m, as follows:

To change the sparse solver being tested, change the value of the parameter "GP.alg". Code for the pcbc-dim solver is included, but to test other solvers you should install the small-box toolbox and ensure that the solvers you wish to test are on your matlab path.

To perform classification using a single dictionary (as used by Wright et al 2009b), set the parameter "GP.network" equal to 'single'. To perform classification using multiple sub-dictionaries (as used by Sprechmann and Sapiro, 2010), set the parameter "GP.network" equal to 'subnets'.

To predefine the dictionary using the training exemplars, set parameter "GP.dictionary" equal to 'all'. To learn class-specific sub-dictionaries, using the ILS-DLA algorithm, set parameter "GP.dictionary" equal to 'learn'.

To change the way the dictionary elements and signals are normalised, change the value of the parameter "GP.dict_norm" (valid values are 1, 2, and Inf).

To change the classification task, modify parameters "GP.data_set" and "GP.imDims".