iteration process in fig5 this element is expressed by an 1 u00d7 d row vector y i y il y i2 y id 0095 fig1 is an illustration showing a structure of the normalizing parameter data file in fig1 the reference numerals 451 1 451 2 451 n correspond to normalizing parameter data d consisting of n in number of data the i th element 451 i corresponds to an output value of the normalizing parameter by the feature extracting means 230 in the i th iteration process in fig5 using the foregoing definitions an implementation of feature extraction in the shown embodiment will be explained the term document matrix updating means 210 reads out x from the term document matrix data file 100 only when i 1 namely in the first iteration process to store in a t u00d7 d matrix e without performing any arithmetic operation accordingly e e 1 e 2 e d e j e j1 e j2 e jt x j1 x j2 x jt u2032 in order to prevent redundant extraction of the features extracted in the preceding iteration processes e is updated in the i th iteration using the current value and the basis vector calculated in the immediately preceding iteration process the result of updating is transferred to the basis vector calculating means 220 a value of e in the i th iteration e i will be expressed by the following expression 5 e ue8a0 i x for ue89e ue89e.