Enum SurvivalTimeBasisConfig 

pub enum SurvivalTimeBasisConfig {
    None,
    Linear,
    BSpline {
        degree: usize,
        knots: Array1<f64>,
        smooth_lambda: f64,
    },
    ISpline {
        degree: usize,
        knots: Array1<f64>,
        keep_cols: Vec<usize>,
        smooth_lambda: f64,
    },
}

Variants

None

Linear

BSpline

Fields

degree: usize

knots: Array1<f64>

smooth_lambda: f64

ISpline

I-spline value rows on the log(t) axis with non-negative coefficients (γ ≥ 0) enforcing structural monotonicity of q(t) = I_basis(log t) · γ. This replaces the row-wise D β + o ≥ guard derivative-guard constraints the marginal-slope family previously relied on.

The design builder lives below at _build_time_block’s SurvivalTimeBasisConfig::ISpline arm and exposes:

• x_entry_time / x_exit_time — I-spline value rows on the log(t) axis. Non-negative entries plus γ ≥ 0 give a monotone-non-decreasing q(t), the structural property the marginal-slope family needs.
• x_derivative_time — right-cumulative B-spline-derivative on log(t) scaled by 1/t, again non-negative with γ ≥ 0, so q'(t) ≥ 0 pointwise. The derivative_guard constant is added externally by add_survival_time_derivative_guard_offset, leaving the derivative guarantee q'(t) ≥ guard exact.
• 2nd-difference penalty on the underlying degree-(k+1) B-spline coefficients, filtered through keep_cols for identifiability.

TimeBlockInput::time_monotonicity declares to the consuming family how monotonicity is enforced. The marginal-slope construction site sets it to crate::survival::location_scale::TimeBlockMonotonicity::StructuralISpline so the family skips row-wise D β + o ≥ guard constraint generation and treats γ ≥ 0 as the sole derivative-guard mechanism. The universal validate_time_qd1_feasible safety net runs regardless.

An earlier iteration proposed a separate C-spline antiderivative parameterization that put q'(t) in the I-spline space and q(t) in the integral-of-I-spline space. That was mathematically equivalent but a strictly worse fit for the codebase (extra basis degree, an extra antiderivative builder, an extra identifiability path, an extra penalty); it was removed in favor of the canonical I-spline-value path here.

Fields

degree: usize

knots: Array1<f64>

keep_cols: Vec<usize>

smooth_lambda: f64

Trait Implementations

impl Clone for SurvivalTimeBasisConfig

fn clone(&self) -> SurvivalTimeBasisConfig

Returns a duplicate of the value.

fn clone_from(&mut self, source: &Self)

Performs copy-assignment from source.

impl Debug for SurvivalTimeBasisConfig

fn fmt(&self, f: &mut Formatter<'_>) -> Result

Formats the value using the given formatter.