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Summarize number, length, and area of features per area/region

db_summarize.Rd

This function summarizes the number of vector features (for all vector types), the total length of features (for Linestring vectors), and the total area of features (for Polygon vectors) within a set of areas. Both the areas and the vector layers/variables to be summarized should be in a PostGIS database.

Usage

db_summarize(
  con,
  areas,
  variables,
  variable_names,
  area_geom_col = "geom",
  variable_geom_col = "geom",
  areas_cols = c("gid", "name_area"),
  areas_cols_groupby = areas_cols,
  length_unit = c("m", "km")[2],
  area_unit = c("m2", "ha", "km2")[3],
  return_spatial = TRUE,
  verbose = FALSE
)

Arguments

con

Connection to PostGIS.

areas

[character]
Areas/polygons for which the summary will be made. It should be in the format "schema_name.table_name", representing a layer located within the PostGIS database.

variables

[vector,character]
Array of layer names to be summarized, such as roads, houses, etc. Layers should be presented in the format "schema_name.layer_name", representing layers located within the PostGIS database.

variable_names

[vector,character]
Names of the variables for the output summary table, corresponding to the variables parameter. This should be an array with the same length as variables.

area_geom_col

[character="geom"]
Character representing the name of the geometry column to be considered for the areas layer.

variable_geom_col

[vector,character="geom"]
Character representing the name of the geometry column to be considered for the variables layers. Alternatively, it can be an array the same length as variables, with the geometry column name for each of the variables.

areas_cols

[vector,character=c("gid", "name_area")]
Array of strings with the name of the columns that should represent the area ID, to define each of the areas in the areas layer.

areas_cols_groupby

[vector,character]
Array of strings with the name of the columns that should used for grouping by the statistics. Typically (and by default) this is the same as area_cols.

length_unit

[character="m"]{"m", "km"}
Unit for summarizing the length of the Linestring vectors. By default, "m" (meters).

area_unit

[character="km2"]{"m2", "ha, "km2"}
Unit for summarizing the area of the Polygon vectors. By default, "km2" (square kilometers).

return_spatial

[logical(1)=TRUE]
If TRUE (default), the results is vector of areas with the summaries for amount, length, and area of layers in the attribute table. If FALSE, the function returns only a data.frame with area names and summary values, but no spatial component.

verbose

[logical(1)=FALSE]⁠
Should messages of the computation steps be printed in the prompt along the computation? Default is FALSE.

Value

If return_spatial = TRUE (default), the the function produces a vector of areas with the summaries for amount, length, and area of layers in the attribute table. The geometry column is the same geometry from the areas layer. If return_spatial = FALSE, the function returns only a data.frame with area names and summary values, but no spatial component.

Examples

areas <- "sam_wrein_ancillary.reindeer_areas_official_2023"
variables <- c("sam_env.cabins_private_no", "sam_env.roads_private_renrein_no",
               "sam_env.reservoirs_all_no")
variable_names <- c("cabins_private", "roads_private", "reservoirs")
variable_geom_col <- c("geom", "geom", "geom_etrs33")
(summ <- db_summarize(con, areas, variables, variables_names,
                      variable_geom_col = variable_geom_col,
                      return_spatial = FALSE,
                      verbose = TRUE))
#> Error in h(simpleError(msg, call)): error in evaluating the argument 'conn' in selecting a method for function 'dbGetQuery': object 'con' not found