Creates an ss_tbl object of type "grd" (SaTScan Grid File).
A grid file specifies the set of candidate centroids at which SaTScan
evaluates potential clusters. When a grid is supplied, SaTScan scans only
at these grid points (rather than at every observed location), which can
reduce computation and enforce a user-defined scanning lattice.
This constructor records the coordinate columns (and optional constraints)
without modifying the input data. Coordinate ordering rules match ss_geo
and are applied by the writer when producing the SaTScan ASCII file.
Usage
ss_grd(
data,
coord1,
coord2,
z = NULL,
earliest_start = NULL,
latest_start = NULL,
earliest_end = NULL,
latest_end = NULL,
grid_variant = "basic"
)Arguments
- data
A data frame containing grid locations.
- coord1
Column name for the first coordinate.
- coord2
Column name for the second coordinate.
- z
Optional column name for Z-coordinate.
- earliest_start
Optional column for earliest start time constraint.
- latest_start
Optional column for latest start time constraint.
- earliest_end
Optional column for earliest end time constraint.
- latest_end
Optional column for latest end time constraint.
- grid_variant
Variant of grid file ("basic", etc.).