In pattern recognition, irreducible testors have been used for feature selection. A number of exhaustive algorithms that find irreducible testors have been reported in the literature. One of the latest and more efficient algorithms reported is YYC, an incremental algorithm that finds all the irreducible testors from a training matrix. Its efficiency relies on building a smaller number of feature combinations by finding compatible sets from the top of the matrix to the current row. Nevertheless, as the number of sets currently found grows, YYC execution becomes too slow. This work proposes two improvements of YYC algorithm, incorporated in a pre-processing phase; additionally, a parallel version is implemented. The paper presents some experimental results using synthetic and real data.

Attribute reduction is a very important task in Rough Set Theory. In this context, in recent years several attribute reduction algorithms based on the discernibility matrix have been proposed. In this paper, we go back to the binary discernibility matrix and reformulate some basic concepts that all ow us to build on them an algorithm for computing reducts. The proposed algorithm takes advantage of the binary representation used for the discernibility matrix and depending on the fulfillment of certain pruning properties several candidates can be jumped (pruned). In this way, the number of candidates to be tested is reduced. Additionally, from the binary discernibility matrix, we define a more compact and ordered matrix, which allows reducing even more the amount of candidates to be evaluated, and the cost of verifying each one of them. The proposed algorithm is able to compute all the reducts of an information table, but it can also be used to find a reduct, or a certain number of them. Experiments over standard datasets show that our algorithm has a good performance.

Typical testors are useful tools for feature selection and for determining feature relevance in supervised classification problems. Nowadays, computing all typical testors of a training matrix is very expensive; all reported algorithms have exponential complexity depending on the number of columns in the matrix. In this paper, we introduce the faster algorithm BR (Boolean Recursive), called fast-BR algorithm, that is based on elimination of gaps and reduction of columns. Fast-BR algorithm is designed to generate all typical testors from a training matrix, requiring a reduced number of operations. Experimental results using this fast implementation and the comparison with other state-of-the-art related algorithms that generate typical testors are presented.

Decision trees are commonly used in supervised classification. Currently, supervised classification problems with large training sets are very common, however many supervised classifiers cannot handle this amount of data. There are some decision tree

In developed countries, especially over the last decade, there has been an explosive growth in the capability to generate, collect and use very large data sets. The objects of these data sets could be simultaneously described by quantitative and qualitative attributes. At present, algorithms able to process either very large data sets (in metric spaces) or mixed (qualitative and quantitative) incomplete data (missing value) sets have been developed, but not for very large mixed incomplete data sets. In this paper we introduce a new clustering method named GLC+ to process very large mixed incomplete data sets in order to obtain a partition in connected sets.