Places non-overlapping rectangular quadrats using a regular grid that tiles the extent of the input domain. Candidate cells are generated with sf::st_make_grid() using the requested quadrat width and height. Cells that fall entirely inside the domain (via sf::st_within(..., sparse = FALSE)) are kept as valid locations, from which up to n_quadrats are sampled at random (set a seed for reproducibility). Because candidates come from a grid, selected quadrats never overlap.
Arguments
- domain
An sf polygon or multipolygon object defining the sampling region. Must have a valid CRS suitable for linear measurements (projected, not geographic).
- n_quadrats
Integer (≥1). The target number of quadrats to place. If fewer valid grid cells exist inside domain, the function will place the maximum possible and adjust this value downward with a warning.
- quadrat_size
Numeric vector of length 2, c(width, height), giving the quadrat dimensions in the same units as domain (e.g., meters). Both values must be positive and finite.
Value
An sf object (polygons) with two columns:
- quadrat_id
Sequential integer identifier of the placed quadrats.
- geometry
Polygon geometry of each quadrat.
Details
The function assumes a planar (projected) CRS where distances and areas are in linear units; if your domain is in longitude/latitude, reproject it first (e.g., to UTM).
quadrat_size is passed to sf::st_make_grid(cellsize = ...), so the two numbers are interpreted as width and height in the domain’s units.
If fewer than n_quadrats valid cells fit entirely inside the domain, the function places as many as possible and emits a warning.
Returned quadrats are labeled sequentially in the order they are sampled (quadrat_id = 1, 2, …, n_quadrats).
See also
place_quadrats (random non-overlapping),
place_quadrats_systematic (grid centers within domain),
place_quadrats_transect (along parallel transects),
place_quadrats_voronoi (via Voronoi cells)