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Initialize Allocation Parameters Table

Source: R/alloc_params_t.R
create_alloc_params_t.Rd

Computes allocation parameters for all viable transitions, aggregated across observed periods and then randomly perturbed N times. This is a method on evoland_db that analyzes patch dynamics to determine expansion vs. patcher behavior for the Dinamica allocation procedure.

The method first computes parameters for all viable transitions across observed periods (where id_period > 1 and is_extrapolated == FALSE), then aggregates (mean) these parameters by transition. Finally, it creates randomly perturbed versions of these aggregated parameters and returns them together with the original estimate, i.e. the result set size is (n viable transitions) * (m perturbations + 1)

Arguments

n_perturbations

Integer number of perturbed parameter sets to generate per transition (default: 5)

sd

Standard deviation for random perturbation of frac_expander as a fraction (default: 0.05)

Value

Invisibly returns the computed alloc_params_t table.

Details

The workflow is:

  1. For each transition and period pair:

    • Create rasters for the anterior and posterior periods

    • Identify transition cells (cells that changed from anterior to posterior class)

    • Use focal operations to determine if transition cells are adjacent to existing patches (expansion) or form new patches (patcher behavior)

    • Compute patch statistics using internal C++ implementation

  2. Aggregate parameters across periods (mean) for each transition

  3. For each transition, create N randomly perturbed versions:

    • Add random noise to frac_expander (normal distribution, mean=0, sd=sd)

    • Clamp frac_expander to [0, 1]

    • Recalculate frac_patcher as 1 - frac_expander

  4. Store all perturbed versions in the alloc_params_t table

Requirements

  • coords_t must have resolution and epsg metadata

  • trans_meta_t must have at least one viable transition

  • periods_t must have at least one observed period with id_period > 1

Examples

if (FALSE) { # \dontrun{
db <- evoland_db$new("path/to/db")
# ... populate with coords, periods, lulc_data, trans_meta ...
db$create_alloc_params_t()
} # }