Skip to contents

Visualize exposure to values in a map

Source: R/fire_exp_extract_map.R
fire_exp_extract_map.Rd

fire_exp_extract_map() standardizes the visualization of outputs from fire_exp_extract() as a map by classifying exposure into predetermined exposure classes.

The plot is returned as a tmap object which can be further customized using tmap commands or exported/saved to multiple image file formats. See tmap::tmap_save() for export details.

Usage

fire_exp_extract_map(
  values_ext,
  classify = c("local", "landscape", "custom"),
  class_breaks,
  method = c("max", "mean"),
  title = "Classified Exposure to Values"
)

Arguments

values_ext

Spatvector of points or polygons from fire_exp_extract()

classify

character, either "local", "landscape", or "custom", to specify classification scheme to use. The default is "local". If set to "custom": the parameter class_breaks must be used.

class_breaks

vector of numeric values between 0-1. Ignored unless classify = "custom". See details.

method

character, either "max" or "mean". If values_ext are polygons the default is "max".This parameter is ignored when values_ext are point features.

title

(Optional) String. Ignored when map = FALSE. A custom title for the plot. The default is "Classified Exposure to Values"

Value

a map is returned as a tmap object

Details

This function visualizes the outputs from fire_exp_extract() with classes. Classes can be chosen from the pre-set "local" and "landscape" options, or customized. To use a custom classification scheme, it should be defined with a list of numeric vectors defining the upper limits of the breaks. A Nil class is added automatically for exposure values of exactly zero.

Local classification breaks are predefined as c(0.15, 0.3, 0.45, 1):

  • Nil (0)

  • 0 - 0.15

  • 0.15 - 0.3

  • 0.3 - 0.45

  • 0.45 - 1

#' Landscape classification breaks are predefined as c(0.2, 0.4, 0.6, 0.8, 1):

  • Nil (0)

  • 0 - 0.2

  • 0.2 - 0.4

  • 0.4 - 0.6

  • 0.6 - 0.8

  • 0.8 - 1

Spatial reference

This function dynamically pulls map tiles for a base map. The crs is set automatically. See tmap::tm_crs() for details.

Examples

# read example hazard data
hazard_file_path <- "extdata/hazard.tif"
hazard <- terra::rast(system.file(hazard_file_path, package = "fireexposuR"))

# read example area of interest
polygon_path <- system.file("extdata", "polygon.shp", package ="fireexposuR")
aoi <- terra::vect(polygon_path)

# generate random points within the aoi polygon
points <- terra::spatSample(aoi, 20)

# compute exposure
exposure <- fire_exp(hazard)

values_exp <- fire_exp_extract(exposure, points)

# visualize example points in standardized map
fire_exp_extract_map(values_exp)
#> [plot mode] fit legend/component: Some legend items or map compoments do not
#> fit well, and are therefore rescaled.
#> ℹ Set the tmap option `component.autoscale = FALSE` to disable rescaling.