Detects a condition for classification of data. Apparatus detects a set of some constituents as a factor of the classification. Apparatus has means for selecting a pattern which is a set of constituents; means of selecting a second pattern formed of the first pattern and at least one constituent added to the first pattern; means of generating an evaluation value for a measure of classification of the plurality of objects under a condition including the first pattern but not the second pattern on the basis of the number of objects satisfying the classification condition in the plurality of objects classified into the first group and the number of objects satisfying the classification condition in the objects classified into the second group; and means of outputting the first and second patterns as a factor of classification when the measure indicated by the evaluation value exceeds a reference measure.