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Fits an accelerated failure time regression to left-censored durations: lifelines' fit_left_censoring.

public static AftSummary FitLeftCensored(AftModel model, ReadOnlySpan<double> design, ReadOnlySpan<double> durations, ReadOnlySpan<bool> eventObserved, int featureCount, AftOptions options = null)

public static AftSummary FitLeftCensored(AftModel model, ReadOnlySpan<double> design, ReadOnlySpan<double> durations, ReadOnlySpan<bool> eventObserved, ReadOnlySpan<double> weights, ReadOnlySpan<double> entries, int featureCount, AftOptions options = null)

The second overload takes lifelines' weights_col and entry_col.

Parameters — model, design, featureCount and options are Fit's. durations holds one positive, finite duration per subject. eventObserved is true where the duration is the event's own time, and false where the event had already happened by it. weights holds one positive, finite weight per subject, or is empty for ones; entries each subject's entry time, non-negative and at most its duration, or is empty for none.

Returns — an AftSummary, as Fit returns.

Exceptions — ArgumentException when the spans do not match the subjects, a value is not finite, a duration is not positive, a weight or entry span is neither empty nor one valid value per subject, or the primary parameter has no column at all. ArgumentOutOfRangeException when model names no model, or featureCount is negative. InvalidOperationException when the fit does not converge, or its parameters are not identified. ArgumentException naming featureCount also when the parameters are more than one array holds, and naming design when the design is more cells than one array holds or its length only matches the subjects times featureCount once that product wraps int (#1614).

Example — readings under a detection limit, against a dose.

using Lodestar.Survival;

double[] dose = [1.0, 2.0, 0.5, 3.0, 0.0, 1.5, 0.0, 2.5, 1.0, 0.5];
double[] readings = [3, 5, 2, 8, 4, 6, 1, 7, 5, 9];
bool[] exact = [true, false, true, true, false, true, false, true, true, true];

AftSummary fit = AcceleratedFailureTime.FitLeftCensored(AftModel.Weibull, dose, readings, exact, featureCount: 1);

double perUnit = Math.Round(fit.Coefficients[0], 6);          // => 0.265103
double concordance = Math.Round(fit.ConcordanceIndex, 6);     // => 0.692308

Remarks — a left-censored subject contributes 1 − S(t) at its own linear predictors, as in ParametricSurvival.FitLeftCensored. The concordance index is lifelines': the durations against the predicted medians, a duration without an observed event counted as a censoring, as lifelines counts it.

Applies to — net10.0, netstandard2.0.

See also — AcceleratedFailureTime, AcceleratedFailureTime.Fit, AftSummary.