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CoxBaseline

One stratum's baseline of a Cox fit: Breslow's hazard at each time, accumulated, and the survival it implies. CoxSummary.Baselines holds one per stratum.

public sealed record CoxBaseline(int Stratum, double[] Times, double[] Hazard, double[] CumulativeHazard, double[] Survival)

Properties — Stratum is the stratum's label, zero for an unstratified fit. Times are every distinct duration of the fit, ascending, as lifelines indexes its baseline. Hazard is the baseline hazard at each, zero where the stratum has no event; CumulativeHazard its running sum; Survival exp(−CumulativeHazard).

Example — the first steps of an unstratified baseline.

using Lodestar.Survival;

double[] design = [1.0, 0.0, 2.0, 1.0, 1.5, 0.0, 3.0, 1.0, 2.5, 0.0,
                   0.5, 1.0, 2.0, 0.0, 1.0, 1.0, 3.5, 0.0, 0.5, 1.0];
double[] months = [12, 5, 20, 3, 15, 9, 8, 14, 2, 18];
bool[] died = [true, true, false, true, true, true, true, false, true, true];

CoxBaseline baseline = CoxProportionalHazards.Fit(design, months, died, featureCount: 2).Baselines[0];

double firstTime = baseline.Times[0];                          // => 2
double atFive = Math.Round(baseline.CumulativeHazard[2], 6);   // => 0.237236

Remarks — the baseline is that of a subject at the covariates' means, as lifelines centres them; a subject's own cumulative hazard is this one times its partial hazard exp((x − mean) · β), which is what CoxSummary.PredictCumulativeHazard computes. Equality compares the label and the four arrays element by element.

The four arrays are taken and exposed as they are, not copied: writing to one changes this record and what it equals, and every holder of the same array, a with copy included (#1305). It never changes a prediction: the CoxSummary the baseline came from predicts from a copy it took when it was fitted (#1304).

Applies to — net10.0, netstandard2.0.

See also — CoxSummary.

Members

Member	What it does
CoxBaseline.Equals	Compares the label and the four arrays, element by element.
CoxBaseline.GetHashCode	A hash consistent with it.