Convert a data.frame of boundary points into a SpatialPolgonsDataFrame

A polygon can be described as a sequence of points defining the polygon's boundary. When given such a sequence (anti clockwise!) this function creates a SpatialPolygonsDataFrame or sf holding the polygon decribed. By default, the first two columns of data are assumed to define the x and y coordinates of the points. This behaviour can be changed using the cols parameter, which points out the names of the columns holding the coordinates. The coordinate reference system of the resulting spatial polygon can be set via the crs parameter. Posterior conversion to a different CRS is supported using the to.crs parameter.

Usage

spoly(
  data,
  cols = colnames(data)[1:2],
  crs = fm_crs(),
  to.crs = NULL,
  format = c("sp", "sf")
)

Arguments

data: A data.frame of points describing the boundary of the polygon (unique points, no holes)
cols: Column names of the x and y coordinates within the data
crs: Coordinate reference system of the points
to.crs: Coordinate reference system for the SpatialLines/sf ouput.
format: Format of the output object. Either "sp" (default) or "sf"

Value

sp::SpatialPolygonsDataFrame or sf::sf

Examples

# \donttest{
# Create data frame of boundary points (anti clockwise!)
pts <- data.frame(
  x = c(1, 2, 1.7, 1.3),
  y = c(1, 1, 2, 2)
)

# Convert to sf
pol <- spoly(pts, format = "sf")

if (require(ggplot2, quietly = TRUE)) {
  # Plot it!
  ggplot() +
    gg(pol)
}

# }