Package 'geogrid'

Assign the polygons in the original spatial data to their new location.

Description

Assigns each polygon in the original file to a new location in the gridded geometry using the Hungarian algorithm.

Usage

assign_polygons(shape, new_polygons)

## S3 method for class 'SpatialPolygonsDataFrame'
assign_polygons(shape, new_polygons)

## S3 method for class 'sf'
assign_polygons(shape, new_polygons)

Arguments

shape	A "SpatialPolygonsDataFrame" or an sf object representing the original spatial polygons.
new_polygons	A "geogrid" object returned from calculate_grid.

Value

An object of the same class as shape

Examples

library(sf)
input_file <- system.file("extdata", "london_LA.json", package = "geogrid")
original_shapes <- st_read(input_file) %>% st_set_crs(27700)

# calculate grid
new_cells <- calculate_grid(shape = original_shapes,
  grid_type = "hexagonal", seed = 1)
grid_shapes <- assign_polygons(original_shapes, new_cells)
plot(grid_shapes)

par(mfrow = c(1, 2))
plot(st_geometry(original_shapes))
plot(st_geometry(grid_shapes))

## Not run: 
# look at different grids using different seeds
par(mfrow=c(2, 3), mar = c(0, 0, 2, 0))
for (i in 1:6) {
  new_cells <- calculate_grid(shape = original_shapes,
    grid_type = "hexagonal", seed = i)
  plot(new_cells, main = paste("Seed", i, sep=" "))
}

## End(Not run)

---

Calculate size of grid items (deprecated).

Description

Given an input multipolgyon spatial data frame this function calculates the required cell size of a regular or hexagonal grid.

Usage

calculate_cell_size(
  shape,
  shape_details = NULL,
  learning_rate = 0.03,
  grid_type = c("hexagonal", "regular"),
  seed = NULL,
  verbose = FALSE
)

Arguments

shape	A 'SpatialPolygonsDataFrame' object representing the original spatial polygons.
shape_details	deprecated.
learning_rate	The rate at which the gradient descent finds the optimum cellsize to ensure that your gridded points fit within the outer boundary of the input polygons.
grid_type	Either 'hexagonal' for a hexagonal grid (default) or 'regular' for a regular grid.
seed	An optional random seed integer to be used for the grid calculation algorithm.
verbose	A logical indicating whether messages should be printed as the algorithm iterates.

---

Calculate grid from spatial polygons.

Description

Given an input multipolgyon spatial data frame this function calculates a hexagonal or regular grid that strives to preserve the original geography.

Usage

calculate_grid(
  shape,
  learning_rate = 0.03,
  grid_type = c("hexagonal", "regular"),
  seed = NULL,
  verbose = FALSE
)

## S3 method for class 'SpatialPolygonsDataFrame'
calculate_grid(
  shape,
  learning_rate = 0.03,
  grid_type = c("hexagonal", "regular"),
  seed = NULL,
  verbose = FALSE
)

## S3 method for class 'sf'
calculate_grid(
  shape,
  learning_rate = 0.03,
  grid_type = c("hexagonal", "regular"),
  seed = NULL,
  verbose = FALSE
)

Arguments

shape	A 'SpatialPolygonsDataFrame' or an sf object representing the original spatial polygons.
learning_rate	The rate at which the gradient descent finds the optimum cellsize to ensure that your gridded points fit within the outer boundary of the input polygons.
grid_type	Either 'hexagonal' for a hexagonal grid (default) or 'regular' for a regular grid.
seed	An optional random seed integer to be used for the grid calculation algorithm.
verbose	A logical indicating whether messages should be printed as the algorithm iterates.

Examples

library(sf)
input_file <- system.file('extdata', 'london_LA.json', package = 'geogrid')
original_shapes <- st_read(input_file) %>% st_set_crs(27700)

# calculate grid
new_cells <- calculate_grid(shape = original_shapes,
  grid_type = 'hexagonal', seed = 1)
grid_shapes <- assign_polygons(original_shapes, new_cells)
plot(grid_shapes)

par(mfrow = c(1, 2))
plot(st_geometry(original_shapes))
plot(st_geometry(grid_shapes))

## Not run: 
# look at different grids using different seeds
par(mfrow=c(2, 3), mar = c(0, 0, 2, 0))
for (i in 1:6) {
  new_cells <- calculate_grid(shape = original_shapes,
    grid_type = 'hexagonal', seed = i)
  plot(new_cells, main = paste('Seed', i, sep=' '))
}

## End(Not run)

---

Extract details from provided polygons (deprecated).

Description

Extract spatial extent, range and other geospatial features from the output of read_polygons. Items are returned as a list for use in calculate_grid.

Usage

get_shape_details(input_shape)

Arguments

input_shape

A "SpatialPolygonsDataFrame" object representing the original spatial polygons.

---

Extract details from provided polygons.

Description

Extract spatial extent, range and other geospatial features from the output of read_polygons. Items are returned as a list for use in calculate_grid.

Usage

get_shape_details_internal(input_shape)

Arguments

input_shape

A "SpatialPolygonsDataFrame" object representing the original spatial polygons.

---

hungarian_cc

Description

hungarian_cc

Usage

hungarian_cc(cost)

Arguments

cost	cost matrix

---

hungariansafe_cc

Description

hungariansafe_cc

Usage

hungariansafe_cc(cost)

Arguments

cost	cost matrix

---

Plot a 'geogrid' object

Description

Plot a 'geogrid' object

Usage

## S3 method for class 'geogrid'
plot(x, y, ...)

Arguments

x	An object of class 'geogrid' to plot.
y	ignored
...	Additional parameters passed to the 'sp' package's plot method.

---

Import spatial data.

Description

Simple function to read spatial data into a SpatialPolygonsDataFrame. Based on st_read from package sf.

Usage

read_polygons(file)

Arguments

file	A file path pointing to a shapefile or GeoJSON file, or a character string holding GeoJSON data. See the dsn argument of st_read for more details.

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