Data SGP & Data HK preparation and differences
There a two common formats for representing longitudinal (time-dependent) student assessment data: WIDE and LONG format. For WIDE format data, each case/row represents a unique student, and columns represent variables associated with the student at different times. For LONG format data, time-dependent data for the student is spread out across multiple rows in the data set. The Data SGP, installed when one installs the SGP package, includes exemplar WIDE and LONG data sets (sgpData and sgpData_LONG, respectively) to assist in setting up your data.
Deciding whether to format in WIDE or LONG format is driven by many conditions. In terms of the analyses that can be performed using the SGP package, the WIDE data format is used by the lower-level functions
studentGrowthProjections whereas the higher-level wrapper functions utilize the LONG data format. For all but the simplest, one-off, analyses, you’re likely better off formatting your data in the LONG format and using the higher-level functions. This is particularly true when Data HK is installed operational for a year where LONG data has numerous preparation and storage benefits over WIDE data.