View source: R/calculate_grid.R

calculate_grid | R Documentation |

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

```
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
)
```

`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. |

```
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)
```

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