A feature-converting device that provides good features quickly. The device includes first and second feature construction units and first and second feature selection units. The first feature construction unit receives one or more first features and constructs one or more second features that represent the results of applying a unary function to the respective first features. The first feature selection unit computes relevance between the first and second features and a target variable that includes elements associated with elements included in the first features and selects one or more third features that represent highly relevant features. The second feature construction unit constructs one or more fourth features that represent the results of applying a multi-operand function to the third features. The second feature selection unit computes the relevance between the third and fourth features and the target variable and selects at least one fifth feature that represents highly relevant features.
Please help me write a proper abstract based on the patent claims. CLAIM: 1. A feature-converting device comprising: a first feature construction unit configured to receive one or more first features representing features including one or more elements composed of a numeral or a code, and construct, by applying one or more unary functions that compute at least one of the features on the basis of at least one of the features to the received first features, one or more second features representing results of applying the unary operation functions to the first features; a first feature selection unit configured to compute relevance between (i) the one or more second features and the one or more first features and (ii) a target variable that includes one or more elements composed of a numeral or a code associated with one or more of the elements included in the first features, and select one or more third features representing highly relevant features from among the one or more second features and the one or more first features; a second feature construction unit configured to receive the one or more third features and applying one or more kinds of multi-operand functions, which compute at least one of the features on the basis of one or more of the features, to the received third features, and constructing one or more fourth features representing the results of applying the multi-operand functions to the third features; and a second feature selection unit configured to compute relevance between (iii) the one or more of the fourth features and the one or more third features and (iv) the target variable, and select at least one fifth feature that represents highly relevant feature from among the one or more of the fourth features and the one or more third features. 2. The feature-converting device according to claim 1, wherein the second feature construction unit applies, of the multi-operand functions, a multi-operand function that computes at least one of the features on the basis of two of the features to the third features. 3. The feature-converting device according to claim 2, wherein the second feature construction unit applies, to the third features, second arithmetic processing that computes one of the features on the basis of one or more of the features and additionally can be applied to each of the elements constituting the features. 4. The feature-converting device according to claim 1, comprising: third feature construction unit configured to compute one or more sixth features by applying a third arithmetic processing that computes one or more of the features on the basis of at least one or more of the features to the first features, the third features, or the fifth features; and third feature selection unit configured to compute correlation of the one or more sixth features, the one or more of the fourth features, and the one or more second features with the target variable, and select at least one seventh feature that represents highly relevant features from among the one or more sixth features, the one or more of the fourth features and the one or more second features. 5. A learning device comprising: the feature-converting device according to claim 1; and learning unit configured to receive learning information in which one or more of the features are associated with the target variable, and execute learning operation or predictive operation on the basis of the features computed by the feature-converting device, wherein the first feature construction unit receives the features included in the learning information as the first features. 6. A feature-conversion method comprising causing an information processing device to: receiving one or more first features representing features including one or more elements composed of a numeral or a code, and constructing, by applying one or more unary functions that compute at least one of the features on the basis of at least one of the features to the received first features, one or more second features representing results of applying the unary operation functions to the first features; computing relevance between (i) the one or more second features and the one or more first features and (ii) a target variable that includes one or more elements composed of a numeral or a code associated with one or more of the elements included in the first features, and selecting one or more third features representing highly relevant features from among the one or more second features and the one or more first features; receiving the one or more third features and applying one or more kinds of multi-operand functions, that compute at least one of the features on the basis of one or more of the features, to the received third features, and constructing one or more fourth features representing the results of applying the multi-operand functions to the third features; and computing relevance between (iii) the one or more of the fourth features and the one or more third features and (iv) the target variable, and selecting at least one fifth feature that represents highly relevant feature from among the one or more of the fourth features and the one or more third features. 7. A non-transitory recording medium storing a feature-conversion program that causes a computer to realize: a first feature construction function configured to receive one or more first features representing features including one or more elements composed of a numeral or a code, and construct, by applying one or more unary functions that compute at least one of the features on the basis of at least one of the features to the received first features, one or more second features representing results of applying the unary operation functions to the first features; a first feature selection function configured to compute relevance between (i) the one or more second features and the one or more first features and (ii) a target variable that includes one or more elements composed of a numeral or a code associated with one or more of the elements included in the first features, and select one or more third features representing highly relevant features from among the one or more second features and the one or more first features; a second feature construction function configured to receive the one or more third features and applying one or more kinds of multi-operand functions, that compute at least one of the features on the basis of one or more of the features, to the received third features, and construct one or more fourth features representing the results of applying the multi-operand functions to the third features; and a second feature selection function configured to compute relevance between (iii) the one or more of the fourth features and the one or more third features and (iv) the target variable, and select at least one fifth feature that represents highly relevant feature from among the one or more of the fourth features and the one or more third features. 8. The non-transitory recording medium storing the feature-conversion program according to claim 7, wherein the second feature construction function applies, of the multi-operand functions, a multi-operand function that computes at least one of the features on the basis of two of the features to the third features. 9. The non-transitory recording medium storing the feature-conversion program according to claim 7, wherein the second feature construction function applies, to the third features, second arithmetic processing that computes one of the features on the basis of one or more of the features and additionally can be applied to each of the elements constituting the features. 10. A non-transitory recording medium storing a learning program, the learning program causing a computer to realize a learning function configured to receive for receiving learning information in which one or more of the features are associated with the target variable, and execute learning operation or predictive operation on the basis of the features computed according to the feature-conversion program according to claim 7, wherein; the first feature construction function receives the features included in the learning information as the first features.