Abstract: Upon detecting, on a screen that displays first drawing data including two or three category series of first grouped data each associated with different one of categories of the first grouped data, a superimposing operation for superimposing the two or three category series of first grouped data, an apparatus calculates representative values for each of one or two category series of second grouped data that are generated by superimposing at least one category series of first grouped data in accordance with the superimposing operation. The apparatus creates second drawing data including the representative values that are calculated for each of the one or two category series of second grouped data, and displays the second drawing data on the screen.