util_extract_multibuffer: Extract raster values for multiple buffers

In marcosci/landscapetools: Landscape Utility Toolbox

Extract raster values for multiple buffers

Description

This function creates a series of circular buffers around spatial points and computes the frequency of each value of a raster within the buffers; the results are printed in a data.frame.

Usage

util_extract_multibuffer(
  landscape,
  points,
  buffer_width,
  max_width = NULL,
  rel_freq = FALSE,
  fun = NULL,
  point_id_text = TRUE,
  ...
)

Arguments

landscape	Raster* object
points	Point(s) represented by a two-column matrix or data.frame; SpatialPoints*; SpatialPolygons*; SpatialLines; Extent; a numeric vector representing cell numbers; or sf* POINT object.
buffer_width	Buffer widths in which the frequency of landscape values is measured. It might be either a single value or a vector of buffer sizes, if max_width = NULL (default). If a value if provided for max_width, a series of buffer sizes is created, from buffer_width to max_width, with increases of buffer_width.
max_width	Maximum distance to which buffer_width is summed up. If NULL, buffer_width is interpreted as a series of buffer widths.
rel_freq	Logical. If TRUE, the relative frequency of raster values is also returned, besides the absolute frequency. Ignored if fun is provided.
fun	Function to apply to raster values within the buffer (e.g. "median", "mean").
point_id_text	Logical. If TRUE, the string "Point ID:" is added to the first column of the output.
...	additional arguments (none implemented)

Value

A tibble with the frequency of each raster value within the buffers of different sizes around each point. Alternatively, a tibble with the relative frequency of raster values, if rel_freq = TRUE, or a function from the raster values, if fun is provided.

Examples

# create single point
new_point = matrix(c(75,75), ncol = 2)

# show landscape and point of interest
show_landscape(classified_landscape, discrete = TRUE) +
ggplot2::geom_point(data = data.frame(x = new_point[,1], y = new_point[,2]),
                    ggplot2::aes(x = x, y = y),
                    col = "grey", size = 3)

# extract frequency of each pixel value within each buffer from 10 to 50 m width
util_extract_multibuffer(classified_landscape, new_point, 10, 50)
# use irregular buffer sizes
util_extract_multibuffer(classified_landscape, new_point, c(5, 10, 20, 30))
# also returns relative frequency
util_extract_multibuffer(classified_landscape, new_point, 10, 50, rel_freq = TRUE)
# use a given function - e.g. median in each buffer width
util_extract_multibuffer(classified_landscape, new_point, 10, 50, fun = "median")

# show multiple points share
new_points = matrix(c(75, 110, 75, 30), ncol = 2)
util_extract_multibuffer(classified_landscape, new_points, c(5, 10, 20, 30))

marcosci/landscapetools documentation built on Oct. 14, 2022, 3 a.m.