A combination selecting method comprises the following steps: firstly, selecting a fixed number of sources from a plurality of the sources to generate a plurality of predictive combinations; next, filtering the predictive combinations by a parameter to generate a group associating with the predictive combinations satisfied by the parameter; then, altering a part of the sources of each predictive combination to generate a new predictive combination correspondingly from each predictive combination, and filtering the new predictive combinations by the parameter to add into the group; finally, repeating performing the previous step until the total number of all predictive combinations achieves a goal.
Please help me write a proper abstract based on the patent claims. CLAIM: 1. A combination selecting method, comprising the following steps: (A) selecting a fixed number of sources from a plurality of the sources, to generate a plurality of predictive combinations; (B) filtering the predictive combinations by a parameter to generate a group associating with the predictive combinations satisfied by the parameter; (C) altering a part of the sources of each predictive combination to generate a new predictive combination correspondingly from each predictive combination, and filtering the new predictive combinations by the parameter to add into the group; and (D) repeating to perform the step (C) until the total number of all predictive combinations achieves a goal. 2. The combination selecting method according to claim 1, wherein in the step (A), a set having the fixed number of sources is selected according to a random selection or a predetermined combination list with the sources to provide the predictive combinations. 3. The combination selecting method according to claim 1, wherein in the step (D), the goal is a fixed frequency of times or a predetermined number of the predictive combinations within the group. 4. The combination selecting method according to claim 3, further comprising the following step: (F) generating a suggestion table by ordering the predictive combinations and the new predictive combinations of the group based on the parameter. 5. The combination selecting method according to claim 1, wherein in the step (B), a geometric center associated with the predictive combinations of the group, is calculated after the generation of the group. 6. The combination selecting method according to claim 5, wherein in the step (C), the part of the sources of each predictive combination is altered to generate the new predictive combination approximating to the geometric center. 7. The combination selecting method according to claim 6, wherein when the dot product between a vector from each predictive combination to each new predictive combination and another vector from each predictive combination to the geometric center is greater than zero, the new predictive combination is judged to approximate to the geometric center. 8. The combination selecting method according to claim 6, wherein when a distance from each predictive combination to the geometric center is less than another distance from each new predictive combination to the geometric center, the new predictive combination is judged to approximate to the geometric center. 9. The combination selecting method according to claim 5, wherein in the step (C), the part of the sources of each predictive combination is altered to generate the new predictive combination removing from the geometric center. 10. The combination selecting method according to claim 9, wherein when the dot product between a vector from each predictive combination to each new predictive combination and another vector from each predictive combination to the geometric center is less than zero, the new predictive combination is judged to be removing from the geometric center. 11. The combination selecting method according to claim 9, wherein when a distance from each predictive combination to the geometric center is longer than another distance from each new predictive combination to the geometric center, the new predictive combination is judged to be removing from the geometric center. 12. The combination selecting method according to claim 5, wherein the geometric center is a center of gravity or a center of mass. 13. The combination selecting method according to claim 1, wherein after the step (A), a characteristic result of each predictive combination is calculated to compare with the parameter. 14. The combination selecting method according to claim 13, wherein the sources is obtained from coal bunkers. 15. The combination selecting method according to claim 14, wherein a combination with repetition is utilized to perform selecting from the coal bunkers. 16. The combination selecting method according to claim 14, wherein the characteristic result comprises at least one of a density of sulfides (SOx), a density of nitrides (NOx), an amount of ash, an erosion property, an accumulation property, a clinkering property, a quantity of coal, and a capacity of coal feeder. 17. A combination selecting system, comprising: a plurality of storages, configured to store a plurality of sources respectively; a combination selecting device, coupled to the storages, comprising: a source selecting module, configured to select a fixed number of sources from a plurality of the sources to generate a plurality of predictive combinations; and a calculating module, coupled to the source selecting module, configured to filter the predictive combinations by a parameter to generate an group associating with the predictive combinations satisfied by the parameter; configured to alter a part of the sources of each predictive combination to generate a new predictive combination correspondingly from each predictive combination, and filter the new predictive combinations by the parameter to add into the group; and further configured to repeat the previous steps until the total number of all predictive combinations achieves a goal. 18. The combination selecting system according to claim 17, wherein the source selecting module selects a set having the fixed number of sources according to a random selection or a predetermined combination list with the sources to provide the predictive combinations. 19. The combination selecting system according to claim 17, wherein the calculating module calculates a geometric center associated with the predictive combinations of the group after the generation of the group. 20. The combination selecting system according to claim 19, wherein the calculating module alters the part of the sources of each predictive combination to generate the new predictive combination approximating to or removing from the geometric center.