R: sf POLYGON

sf_polygon {sfheaders} | R Documentation

## 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"
    )

[Package sfheaders version 0.2.2 Index]