Extends logistic4() with an asymmetry parameter \(g\):
$$y = a + \frac{d - a}{\bigl(1 +
\exp\!\bigl(-\frac{x - c}{b}\bigr)\bigr)^g}$$
Arguments
- x
Numeric vector. Independent variable (typically log10-concentration).
- a
Numeric scalar. Lower asymptote (baseline response).
- b
Numeric scalar. Scale parameter (\(b > 0\)); controls steepness.
- c
Numeric scalar. Inflection-point location on the x-axis.
- d
Numeric scalar. Upper asymptote (saturation response).
- g
Numeric scalar. Asymmetry parameter (\(g > 0\)).
Details
When \(g = 1\) this reduces to logistic4().
\(g > 1\) skews toward the upper asymptote;
\(0 < g < 1\) skews toward the lower asymptote.
See also
Other forward-models:
gompertz4(),
logistic4(),
loglogistic4(),
loglogistic5()