geometries

Converts a data.frame into a collection of geometries.

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)
)
#> [[1]]
#>      [,1] [,2]
#> [1,]    1   10
#> [2,]    2    9
#> [3,]    3    8
#> [4,]    4    7
#> [5,]    5    6
#> 
#> [[2]]
#>      [,1] [,2]
#> [1,]    6    5
#> [2,]    7    4
#> [3,]    8    3
#> [4,]    9    2
#> [5,]   10    1
#> 

## Adding a class attribute
gm_geometries(
  df
  , id_cols = c(1)
  , geometry_cols = c(2,3)
  , list( class = "my_line_object" )
 )
#> [[1]]
#>      [,1] [,2]
#> [1,]    1   10
#> [2,]    2    9
#> [3,]    3    8
#> [4,]    4    7
#> [5,]    5    6
#> attr(,"class")
#> [1] "my_line_object"
#> 
#> [[2]]
#>      [,1] [,2]
#> [1,]    6    5
#> [2,]    7    4
#> [3,]    8    3
#> [4,]    9    2
#> [5,]   10    1
#> attr(,"class")
#> [1] "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" )
)
#> [[1]]
#> [[1]]
#>      [,1] [,2]
#> [1,]    1   10
#> [2,]    2    9
#> [3,]    3    8
#> 
#> [[2]]
#>      [,1] [,2]
#> [1,]    4    7
#> [2,]    5    6
#> 
#> attr(,"class")
#> [1] "my_multiline_object"
#> 
#> [[2]]
#> [[1]]
#>      [,1] [,2]
#> [1,]    6    5
#> [2,]    7    4
#> 
#> [[2]]
#>      [,1] [,2]
#> [1,]    8    3
#> [2,]    9    2
#> 
#> [[3]]
#>      [,1] [,2]
#> [1,]   10    1
#> 
#> attr(,"class")
#> [1] "my_multiline_object"
#> 

## Using character column names
gm_geometries(
  df
  , id_cols = c("id","id1")
  , geometry_cols = c("x","y")
  )
#> [[1]]
#> [[1]][[1]]
#>      [,1] [,2]
#> [1,]    1   10
#> [2,]    2    9
#> [3,]    3    8
#> 
#> [[1]][[2]]
#>      [,1] [,2]
#> [1,]    4    7
#> [2,]    5    6
#> 
#> 
#> [[2]]
#> [[2]][[1]]
#>      [,1] [,2]
#> [1,]    6    5
#> [2,]    7    4
#> 
#> [[2]][[2]]
#>      [,1] [,2]
#> [1,]    8    3
#> [2,]    9    2
#> 
#> [[2]][[3]]
#>      [,1] [,2]
#> [1,]   10    1
#> 
#> 

## matrix input
m <- as.matrix( df )
gm_geometries(
  m
  , id_cols = c("id","id1")
  , geometry_cols = c("x","y")
  )
#> [[1]]
#> [[1]][[1]]
#>      [,1] [,2]
#> [1,]    1   10
#> [2,]    2    9
#> [3,]    3    8
#> 
#> [[1]][[2]]
#>      [,1] [,2]
#> [1,]    4    7
#> [2,]    5    6
#> 
#> 
#> [[2]]
#> [[2]][[1]]
#>      [,1] [,2]
#> [1,]    6    5
#> [2,]    7    4
#> 
#> [[2]][[2]]
#>      [,1] [,2]
#> [1,]    8    3
#> [2,]    9    2
#> 
#> [[2]][[3]]
#>      [,1] [,2]
#> [1,]   10    1
#> 
#> 

gm_geometries(
  m
  , id_cols = c(1,4)
  , geometry_cols = c(2,3)
 )
#> [[1]]
#> [[1]][[1]]
#>      [,1] [,2]
#> [1,]    1   10
#> [2,]    2    9
#> [3,]    3    8
#> 
#> [[1]][[2]]
#>      [,1] [,2]
#> [1,]    4    7
#> [2,]    5    6
#> 
#> 
#> [[2]]
#> [[2]][[1]]
#>      [,1] [,2]
#> [1,]    6    5
#> [2,]    7    4
#> 
#> [[2]][[2]]
#>      [,1] [,2]
#> [1,]    8    3
#> [2,]    9    2
#> 
#> [[2]][[3]]
#>      [,1] [,2]
#> [1,]   10    1
#> 
#> 

## 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
)
#> [[1]]
#>      [,1] [,2]
#> [1,]    1    1
#> [2,]    1    2
#> [3,]    2    2
#> [4,]    2    1
#> [5,]    1    1
#>