In the case of Data Categories 2, 6, 7, 8, 9 and 10, all input data refers to that associated with a particular structure. Therefore, each structure has its own data category, e.g. if there are three structures being analyzed there will be Data Categories 2.1, 2.2, 2.3, 6.1, 6.2, 6.3, 7.1, 7.2, 7.3 etc. Such a group of data categories (i.e. 2.1, 2.2, 2.3 or 6.1, 6.2, 6.3) is known as a data category series. The data category keyword indicates this by having the structure number incorporated into the data category keyword, e.g. for Data Category 6 (Frequency and Direction Tables) we have, for three structures, FDR1 as the data category keyword for Structure 1, FRD2 as the data category keyword for Structure 2, etc. The documentation will refer to these as Data Category FDR* to mean all three data categories, i.e. the Data Category Series 6.1, 6.2, and 6.3.