ccd_to_theta: Map standardised CCD coordinates to physical hyperparameters

In tulpa: Templated Unified Library for Posterior Approximation in Bayesian Hierarchical Models

Map standardised CCD coordinates to physical hyperparameters

Description

Converts standardised CCD z-coordinates (in \mathbb{R}^k) to physical hyperparameters \theta via the affine map \theta = \hat\theta + L \cdot z with optional log-scale transform per component. L is typically a Cholesky factor of the negative Hessian inverse evaluated at the (working) mode \hat\theta – i.e. it scales z to one posterior standard deviation per axis.

Usage

ccd_to_theta(z, theta_hat, L, log_scale = FALSE)

Arguments

z	Matrix ⁠[n_points x k]⁠ of standardised coordinates from ccd_grid().
theta_hat	Numeric vector of length k: centre of the design, in either physical or log-space (per log_scale).
L	Numeric ⁠[k x k]⁠ matrix: scale/rotation applied to z. Pass diag(sd) for a diagonal axis-aligned grid where sd is the per-axis posterior SD; pass a Cholesky factor to capture correlations between hyperparameters.
log_scale	Logical (or logical vector of length k). If TRUE for component j, theta_hat[j] and column j of the affine transform live on log-scale and are exponentiated afterward (useful for positive parameters like tau). Default FALSE everywhere.

Value

Numeric matrix ⁠[n_points x k]⁠ of physical theta-values.

Examples

g <- ccd_grid(2)
ccd_to_theta(g$z, theta_hat = c(0, 1), L = diag(c(0.5, 0.2)))

tulpa documentation built on Oct. 19, 2026, 5:09 p.m.