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Summarize raster within incremental buffer zones around points

lg_rast.Rd

This function calculates raster values within concentric buffer zones ("doughnuts") around a set of measurement points. It optionally applies a summary function to raster values within each buffer and returns raw values or aggregated summaries.

Usage

lg_rast(
  x,
  y,
  func = NULL,
  dist_seq = NULL,
  mindist = NULL,
  maxdist = NULL,
  incdist = NULL,
  plot_doughnuts = TRUE,
  object_n = 1,
  bg_layer = NULL
)

Arguments

x

An object representing measurement points. Can be an sf object or convertible to sf via internal helper functions.

y

A SpatRaster object from the terra package representing the raster to summarize.

func

Optional. A function or character string specifying how to summarize raster values within each buffer. If NULL, raw cell values are returned. Accepts functions supported by exactextractr::exact_extract or a custom function that takes a numeric vector and returns a single value.

dist_seq

Optional numeric vector of buffer distances. If provided, overrides mindist, maxdist, and incdist.

mindist

The minimum distance, ignored if dist_seq is specified

maxdist

The maximum distance, ignored if dist_seq is specified

incdist

The distance increment, ignored if dist_seq is specified

plot_doughnuts

Logical. If TRUE, plots the doughnut geometries for visual verification. Highly recommended for error checking.

object_n

The measurement point that you want to plot separately. A single or vector of integers.

bg_layer

Background layer to plot along with the objects. Currently only accepts terra::spatRaster.

Value

A list with three elements:

buffer_values

Matrix or vector of raster values (raw or summarized) for each buffer.

buffer_area

Matrix or vector of buffer areas corresponding to each value.

value_parea

Numeric vector of values normalized by buffer area.

Details

Internally, this function:

  1. Converts x to an sf object.

  2. Validates that y is a SpatRaster.

  3. Generates buffer distances using .index_check().

  4. Builds doughnut geometries and extracts raster values using values_within_dist_rast().

  5. Computes value per unit area for each buffer.

See also

values_within_dist_rast, doughnut_builder, doughnut_checker

Examples

if (FALSE) { # \dontrun{
# Example: Summarize mean raster values within 3 buffers around points
lg_rast(x = points_sf, y = raster_layer, func = "mean",
        mindist = 100, maxdist = 300, incdist = 100)
} # }