PRESORTED Keyword (CSSELECT command)

By default, CSSELECT assumes that the active dataset is unsorted. The PRESORTED keyword specifies that the data are sorted in advance, which may improve performance when stratification and/or clustering is requested for a large sample frame.

If PRESORTED is used, the data should be sorted first by all stratification variables then by cluster variables consecutively in each stage. The data can be sorted in ascending or descending order. For example, given a sample plan created using the following CSPLAN syntax, the sample frame should be sorted by region, ses, district, type, and school, in that order.

Example

CSPLAN
  /PLAN OUTFILE='/survey/myfile.csplan'
  /DESIGN STRATA=region ses CLUSTER=district type
  /SAMPLE RATE=.2 MOS=districtsize METHOD=PPS_WOR
  /DESIGN CLUSTER=school 
  /SAMPLE RATE=.3 METHOD=SIMPLE_WOR.

An error occurs if PRESORTED is specified and the data are not sorted in proper order.