The input map data set
must be in a SAS data set format (see About Map Data Sets) and it must
contain these variables:
-
a numeric variable named X that
contains the horizontal coordinates of the map boundary points.
-
a numeric variable named Y that
contains the vertical coordinates of the map boundary points.
-
one or more variables that uniquely
identify the current unit areas in the map. These variables are listed
in the ID statement. Each group of observations with a different
ID variable value is evaluated as a separate unit area.
-
one or more variables that identify
the new unit areas to be created in the output map data set. These
variables are listed in the BY statement.
It might also contain
the variable SEGMENT, which is used to distinguish non-conterminous
segments of the same unit areas. Other variables might exist in the
input map data set, but they do not affect the GREMOVE procedure and
they will not be carried into the output map data set.
