The feature quantity selection vectors, indicating which features among those respecting discrete events are to be selected, are fixed. The feature quantity selection spaces taking discrete features as coordinate axes are divided into each segment, and the number of events contained therein is counted. The segments are arranged in order of diminishing event counts contained therein, and the values for functions evaluating the extent of relevance are scanned in the order of segments for which the segments are arranged from the maximum segment counts in the descending order. When the partial situations determined by selection segment counts that are maximum values take evaluation values as their maximum values, even where the feature quantity selection counts are changed, those partial situations are extracted.