Create Spatial Polygon from Coordinates

splnr_create_polygon() constructs an sf polygon object from a series of longitude and latitude coordinates provided in a tibble.

Usage

splnr_create_polygon(x, cCRS = "EPSG:4326")

Arguments

x

A tibble (or tbl_df) object with at least two columns, typically named x (for longitude) and y (for latitude), representing the vertices of the polygon in sequence. The first and last coordinate pair should be the same to form a closed polygon.

cCRS

A character string specifying the target CRS for the output polygon in an EPSG code format (e.g., "EPSG:4326"). Defaults to "EPSG:4326" (WGS 84).

Value

An sf object representing the created polygon, with the specified CRS.

Details

This utility function simplifies the creation of spatial polygons from a tabular format of coordinates. It takes a tibble where columns 'x' and 'y' represent longitude and latitude, respectively. These coordinates are converted into a matrix, then to an sf polygon, and finally to an sf object with the specified Coordinate Reference System (CRS).

The function assumes that the input coordinates (x) are initially in WGS 84 (EPSG:4326) and then transforms them to the cCRS if a different CRS is specified.

Examples

# Example: Create a simple square polygon
square_coords <- dplyr::tibble(
  x = c(-50, 50, 50, -50, -50),
  y = c(120, 120, 180, 180, 120)
)
simple_polygon <- splnr_create_polygon(x = square_coords)
print(simple_polygon)
#> Simple feature collection with 1 feature and 0 fields
#> Geometry type: POLYGON
#> Dimension:     XY
#> Bounding box:  xmin: -50 ymin: 120 xmax: 50 ymax: 180
#> Geodetic CRS:  WGS 84
#>                         geometry
#> 1 POLYGON ((-50 120, 50 120, ...

# Example: Create a polygon and transform to a different CRS (e.g., a UTM zone)
if (FALSE) { # \dontrun{
# Note: EPSG:32611 is UTM Zone 11N. Ensure it's appropriate for your coordinates.
transformed_polygon <- splnr_create_polygon(x = square_coords, cCRS = "EPSG:32611")
print(transformed_polygon)
} # }