sf_polygon {sfheaders}

sf POLYGON

Description

constructs an sf of POLYGON objects

Usage

sf_polygon(
  obj = NULL,
  x = NULL,
  y = NULL,
  z = NULL,
  m = NULL,
  polygon_id = NULL,
  linestring_id = NULL,
  close = TRUE,
  keep = FALSE,
  list_columns = NULL
)

Arguments

obj

sorted matrix or data.frame

x

x geometry column

y

y geometry column

z

z geometry column

m

m geometry column

polygon_id

column of ids for polygons

linestring_id

column of ids for lines (within polygons)

close

logical indicating whether polygons should be closed. If TRUE, all polygons will be checked and force closed if possible

keep

logical indicating if the non-geometry and non-id columns should be kept. if TRUE you must supply the geometry and id columns, and only the first row of each geometry is kept. See Keeping Properties.

list_columns

vector of column names to turn into a list.

Value

sf object of POLYGON geometries

notes

sfheaders functions do not perform any validity checks on the geometries. Nor do they set Coordinate Reference Systems, EPSG, PROJ4 or precision attributes.

The data.frame and matrices you send into the sfheader functions must be ordered.

Keeping Properties

Setting keep = TRUE will retain any columns not specified as a coordinate (x, y, z, m) or an id (e.g., linestring_id, polygon_id) of the input obj.

You can use list_columns to specify which of the properties will be turned into a list, thus keeping all the values in the column. For columns not specified in list_columns, only the first row of the column is kept

The sf_* functions assume the input obj is a long data.frame / matrix, where any properties are repeated down the table for the same geometry.

Examples

m <- matrix(c(0,0,0,0,1,1), ncol = 2 )
sf_polygon( m )

m <- matrix(c(0,0,0,0,0,1,0,1,1,1,2,2,1,2,3,1,3,4), ncol = 3, byrow = TRUE)
sf_polygon( obj = m )
sf_polygon( obj = m, polygon_id = 1 )
sf_polygon( obj = m, linestring_id = 1 )

sf_polygon( obj = m, linestring_id = 1, polygon_id = 1 )

sf_polygon( obj = m, x = 2, y = 3 )
sf_polygon( obj = m, x = 1, y = 2, z = 3 )
sf_polygon( obj = m, x = 2, y = 3, linestring_id = 1, polygon_id = 1 )

df <- data.frame(
  ml_id = c(1,1,1,1,1,1,1,1,1,2,2,2,2,2,2)
  , l_id = c(1,1,1,2,2,2,3,3,3,1,1,1,2,2,2)
  , x = rnorm(15)
  , y = rnorm(15)
  , z = rnorm(15)
  , m = rnorm(15)
)

sf_polygon( obj = df, x = "x", y = "y")
sf_polygon( obj = df, x = "x", y = "y", z = "z")
sf_polygon( obj = df, x = "x", y = "y", z = "z", m = "m")

sf_polygon( obj = df, x = 2, y = 3)
sf_polygon( obj = df, x = 2, y = 3, z = 4)
sf_polygon( obj = df, x = 2, y = 3, z = 4, m = 5)

sf_polygon( obj = df, polygon_id = "ml_id", linestring_id = "l_id" )
sf_polygon( obj = df, polygon_id = 1, linestring_id = 2 )

## keeping properties
df <- data.frame(
  ml_id = c(1,1,1,1,1,1,1,1,1,2,2,2,2,2,2)
  , l_id = c(1,1,1,2,2,2,3,3,3,1,1,1,2,2,2)
  , x = rnorm(15)
  , y = rnorm(15)
  , z = rnorm(15)
  , m = rnorm(15)
  , val = letters[1:15]
  , stringsAsFactors = FALSE
)

## using keep = TRUE means the first row of all non-geometries are kept
sf_polygon(
  obj = df
  , polygon_id = "ml_id"
  , linestring_id = "l_id"
  , x = "x"
  , y = "y"
  , keep = TRUE
)

## use 'list_column' to specify columns where you want to keep all the values
sf_polygon(
  obj = df
  , polygon_id = "ml_id"
  , linestring_id = "l_id"
  , x = "x"
  , y = "y"
  , keep = TRUE
  , list_columns = "val"
)