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Create synthetic environmental gradients over a spatial domain

Source: R/gradients.R
create_environmental_gradients.Rd

Generates three continuous, spatially autocorrelated environmental gradients — temperature, elevation, and rainfall — over a regular grid covering the specified polygonal study area. The gradients are expressed in both normalised \([0, 1]\) form and scaled to physical units.

Usage

create_environmental_gradients(domain, resolution, noise_level)

Arguments

domain

An sf polygon object defining the extent over which gradients will be computed. Only its bounding box is used in this step.

resolution

Integer ≥ 2; number of grid steps per axis. The output will contain resolution^2 rows.

noise_level

Non-negative numeric; standard deviation of Gaussian noise added independently to each gradient before clipping.

Value

A data.frame with columns:

x, y

Grid point coordinates (same CRS as domain).

temperature, elevation, rainfall

Normalised gradients in \([0, 1]\).

temperature_C

Temperature in degrees Celsius (approx. range: -2 to 28).

elevation_m

Elevation in metres (0–2000).

rainfall_mm

Annual rainfall in millimetres (200–900).

Details

The function:

  1. Derives the bounding box of domain and constructs a regular resolution × resolution grid of points.

  2. Normalises \(x\) and \(y\) coordinates to \([0, 1]\).

  3. Computes:

    • Temperature: weighted linear combination of normalised \(x\) (0.7) and \(y\) (0.3) coordinates.

    • Elevation: decreases radially from domain centre.

    • Rainfall: weighted difference of \(x\) and \(y\) components, rescaled to \([0, 1]\).

  4. Adds Gaussian noise with standard deviation noise_level to each raw gradient before clipping to \([0, 1]\).

  5. Produces scaled versions in common physical units: temperature_C (°C), elevation_m (metres), and rainfall_mm (millimetres/year).

Note that gradients are computed for all grid points within the bounding box of domain; no masking to the polygon interior is applied here. Masking can be done later with st_intersects or similar.

See also

st_bbox, st_intersects

Examples

if (FALSE) { # \dontrun{
domain <- create_sampling_domain()
env <- create_environmental_gradients(domain, resolution = 50, noise_level = 0.05)
head(env)
} # }