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Visualize exposure to values in a summary table or map

Source: R/fire_exp_extract_vis.R
fire_exp_extract_vis.Rd

fire_exp_extract_vis() standardizes the visualization of outputs from fire_exp_extract() as a summary table or a map by classifying exposure into predetermined exposure classes.

Usage

fire_exp_extract_vis(
  values_ext,
  classify = c("local", "landscape", "custom"),
  class_breaks,
  method = c("max", "mean"),
  map = FALSE,
  zoom_level,
  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.

map

Boolean. When TRUE, a map is returned as a ggplot object. The default is FALSE.

zoom_level

(Optional). Numeric. Ignored when map = FALSE. set the zoom level for the base map tile. See details. Defaults if:

  • classify = "local" or "custom" the zoom level default is 12

  • classify = "landscape" the zoom level default is 7

title

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

Value

a summary table is returned as a data frame object, Unless: map = TRUE: a ggplot 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 when map = TRUE. The inputs are projected to WGS 84/Pseudo-Mercator (EPSG:3857) to align them with the map tiles.

Zoom level

The map tile zoom level may need to be adjusted. If the base map is blurry, increase the zoom level. Higher zoom levels will slow down the function, so only increase if necessary. Reference the OpenStreetMap Wiki for more information on zoom levels.

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 geometry
geom_file_path <- "extdata/polygon_geometry.csv"
geom <- read.csv(system.file(geom_file_path, package = "fireexposuR"))

# generate an area of interest polygon with the geometry
aoi <- terra::vect(as.matrix(geom), "polygons", crs = hazard)

# generate random points within the aoi polygon
points <- terra::spatSample(aoi, 200)

# compute exposure
exposure <- fire_exp(hazard)

values_exp <- fire_exp_extract(exposure, points)

# summarize example points in a table
fire_exp_extract_vis(values_exp, classify = "local")
#>   scale method class_range   n  prop
#> 1 local  Point         Nil   1 0.005
#> 2 local  Point    0 - 0.15   5 0.025
#> 3 local  Point  0.15 - 0.3  27 0.135
#> 4 local  Point  0.3 - 0.45  34 0.170
#> 5 local  Point    0.45 - 1 133 0.665

# visualize example points in standardized map
fire_exp_extract_vis(values_exp, map = TRUE)