sf2raster {SUNGEO}

Convert simple features object into regularly spaced raster

Description

This function takes in an sf spatial object (polygon or point) and returns a regularly spaced RasterLayer. Reverse translation option allows users to create an sf polygon object from the regularly spaced RasterLayer. This function can also conver the sf object into a cartogram with a user-specified variable name.

Usage

sf2raster(
  polyz_from = NULL,
  pointz_from = NULL,
  input_variable = NULL,
  reverse = FALSE,
  poly_to = NULL,
  return_output = NULL,
  return_field = NULL,
  aggregate_function = list(function(x) mean(x, na.rm = TRUE)),
  reverse_function = list(function(x) mean(x, na.rm = TRUE)),
  grid_dim = c(1000, 1000),
  cartogram = FALSE,
  carto_var = NULL,
  message_out = TRUE,
  return_list = FALSE
)

Arguments

polyz_from

Source polygon layer. sf object.

pointz_from

Source point layer. sf object.

input_variable

Name of input variable from source layer. Character string.

reverse

Reverse translation from raster layer to sf polygon object (polygon features only). Default is FALSE.

poly_to

Destination polygon layer for reverse conversion. Must be specified if reverse=TRUE. sf object.

return_output

Return output for reverse conversion. Must be specified if reverse=TRUE.

return_field

Return field for reverse conversion. Must be specified if reverse=TRUE.

aggregate_function

Aggregation function to be applied to variables specified in input_variable. Must take as an input a numeric vector x. Function or list of functions. Default is mean.

reverse_function

Aggregation function for reverse conversion. Must be specified if reverse=TRUE. Function or list of functions. Default is mean.

grid_dim

Dimensions of raster grid. Numerical vector of length 2 (number of rows, number of columns). Default is c(1000,1000).

cartogram

Cartogram transformation. Logical. Default is FALSE.

carto_var

Input variable for cartogram transformation. Must be specified if cartogram=TRUE. Character string.

message_out

Print informational messages. Logical. Default is TRUE.

return_list

Return full set of results, including input polygons, centroids and field raster. Default is FALSE. Logical.

Value

If return_list=FALSE (default) and reverse=FALSE (default), returns RasterLayer object, with cell values corresponding to input_variable.

If return_list=TRUE and input layer is polygon, returns a list containing

• "return_output". Output raster, with values corresponding to input_variable. RasterLayer object.

• "return_centroid". Raster of centroids, with values corresponding to input_variable. RasterLayer object.

• "poly_to". Source polygons, with columns corresponding to input_variable and auto-generated numerical ID Field. sf object.

• "return_field". Output raster, with values corresponding to auto-generated numerical ID Field. RasterLayer object.

If return_list=TRUE and input layer is points, returns a list containing

• "return_output". Output raster, with values corresponding to input_variable. RasterLayer object.

• "return_point". Source points, with column corresponding to input_variable.

If reverse=TRUE, returns an sf polygon layer, with columns corresponding to input_variable and auto-generated numerical ID Field.

Examples

# Rasterization of polygon layer.
## Not run: 
data(clea_deu2009)
out_1 <- sf2raster(polyz_from = utm_select(clea_deu2009),
                   input_variable = "to1")
terra::plot(out_1)

## End(Not run)
# Rasterization of point layer
## Not run: 
data(clea_deu2009_pt)
out_2 <- sf2raster(pointz_from = utm_select(clea_deu2009_pt),
                   input_variable = "to1",
                   grid_dim = c(25,25))
terra::plot(out_2)

## End(Not run)
# Cartogram (vote turnout scaled by number of valid votes)
## Not run: 
out_3 <- sf2raster(polyz_from = utm_select(clea_deu2009),
                   input_variable = "to1",
                   cartogram = TRUE,
                   carto_var = "vv1")
terra::plot(out_3)

## End(Not run)
# Polygonization of cartogram raster
## Not run: 
out_4a <- sf2raster(polyz_from = utm_select(clea_deu2009),
                    input_variable = "to1",
                    cartogram = TRUE,
                    carto_var = "vv1",
                    return_list = TRUE)
out_4 <- sf2raster(reverse = TRUE,
                   poly_to = out_4a$poly_to,
                   return_output = out_4a$return_output,
                   return_field = out_4a$return_field)
terra::plot(out_4)

## End(Not run)