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One-phase exponential decay

One-phase exponential decay fits y = (Y0 − Plateau) · exp(−K · x) + Plateau, with half-life ln(2) / K.

What is One-phase exponential decay?

Three parameters: Y0 (initial value at x = 0), Plateau (asymptotic value as x → ∞), K (decay rate constant; half-life = ln 2 / K). The model captures any single-pool exponential decay — drug elimination, radioactive decay, voltage discharge.

When residuals show systematic structure suggesting two pools (PK with both fast and slow clearance phases, biphasic radioactive decay), upgrade to nonlinear_exp_two_phase.

When should I use One-phase exponential decay?

  • Pharmacokinetics (drug clearance from plasma).
  • Radioactive decay.
  • Any single-pool first-order decay process.

What data does it need?

Numeric time X + signal Y.

What does it report?

Y0 + Plateau + K with 95% CIs.

How do I interpret the result?

Report half-life t½ = ln 2 / K with its CI — that's the more clinically interpretable number than K itself.

See also