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Fits the universal-kriging model used by em_gp(). Inputs are already log-transformed single-year observations; the response is log relative biomass. Training and hyperparameter selection must occur outside run_mse(). Rows from the same underlying OM iteration must stay together when creating training and validation sets. This function does not select a design or tune hyperparameters, and never accesses an operating model.

Usage

fit_em_gp(
  data,
  log_status,
  features = c("log_cpue_aw", "log_cpue_ss", "log_catch_total"),
  corr_scale = 0.5,
  nugget = 0.2,
  scaler = NULL,
  target = NULL,
  catch_component = NULL
)

Arguments

data

Data frame containing the named, already transformed features.

log_status

Finite numeric log-status response, one per design row.

features

Names of the supported single-year CPUE/catch features.

corr_scale

Positive common inverse squared length-scale coefficient.

nugget

Non-negative covariance nugget relative to GP variance.

scaler

Optional list with named centre, spread, and features. Estimate it from training data only; omitted means use the supplied design rows.

target

Optional mse_target() describing the training response.

catch_component

Optional catch-component name used in training.

Value

A fitted GP list accepted by em_gp().

Details

The correlation is exp(-corr_scale * squared Euclidean distance) after standardisation. A linear mean, fitted nugget, and emulator's variance estimate reproduce the existing CRA2 GP convention. Intervals are conditional on the supplied hyperparameters, not fully marginal Bayesian intervals.