gm_geometries: geometries

In geometries: Convert Between R Objects and Geometric Structures

Description

Converts a data.frame into a collection of geometries.

Usage

gm_geometries(
  obj,
  id_cols,
  geometry_cols,
  class_attributes = list(),
  close = FALSE,
  closed_attribute = FALSE
)

Arguments

obj	data.frame
id_cols	vector of id columns (either integer or string)
geometry_cols	vector of geometry columns (either integer or string)
class_attributes	class attributes to assign to each geometry
close	logical stating if the last row must equal the first row of each geometry
closed_attribute	logical, if true a 'has_been_closed' attribute is added to each matrix that has been closed.

Value

A list of matrices representing the input object, split by the id column(s).

Examples

df <- data.frame(
  id = c(1,1,1,1,1,2,2,2,2,2)
  , x = 1:10
  , y = 10:1
)

gm_geometries(
  df
  , id_cols = c(1L)
  , geometry_cols = c(2L,3L)
)

## Adding a class attribute
gm_geometries(
  df
  , id_cols = c(1)
  , geometry_cols = c(2,3)
  , list( class = "my_line_object" )
 )

## Adding a second ID column
df$id1 <- c(1,1,1,2,2,1,1,2,2,3)

gm_geometries(
  df
  , id_cols = c(1,4)
  , geometry_cols = c(2,3)
  , list( class = "my_multiline_object" )
)

## Using character column names
gm_geometries(
  df
  , id_cols = c("id","id1")
  , geometry_cols = c("x","y")
  )

## matrix input
m <- as.matrix( df )
gm_geometries(
  m
  , id_cols = c("id","id1")
  , geometry_cols = c("x","y")
  )

gm_geometries(
  m
  , id_cols = c(1,4)
  , geometry_cols = c(2,3)
 )

## use close to make the last row the same as the first row
df <- data.frame(
  id = c(1,1,1,1)
  , x = c(1,1,2,2)
  , y = c(1,2,2,1)
)

gm_geometries(
  df
  , id_cols = "id"
  , geometry_cols = c("x","y")
  , close = TRUE
)

geometries documentation built on Jan. 13, 2021, 8:12 p.m.