b2slope {richards}R Documentation

The slope and the parameter 'b' of Richards curves

Description

Finds the slope at x50 of a Richards curve, or the parameter b of a Richards curve with a given slope. x2c is for finding the parameters C and E from x50.

Usage

b2slope(ny = X[, "ny"], b = X[, "b"], a = X[, "a"], d = X[, "d"], 
        X = NULL, fold = 2, delta = 1e-09)
slope2b(ny = X[, "ny"], slope = X[, "slope"], a = X[, "a"], d = X[, "d"], 
        X = NULL, fold = 2, delta = 1e-09)
ny2f(ny, delta = 1e-09)
x2c(x50 = X[, "x50"], ny = X[, "ny"], b = X[, "b"],
    X = NULL, fold = 2, x50f = 1, delta = 1e-09)

Arguments

ny the shape parameter: affects near which asymptote maximum 'growth' occurs.
b a numeric scale parameter on the input axis, the 'growth rate', the reciprocal of the scale parameter scal for the four point logistic curve by SSfpl. (The 'growth' parameter b should be negative, and a is thus the right side (larger) asymptote, for Bertalenffy growth models.)
slope a numeric parameter representing the slope at x50 of the curve.
a a numeric parameter representing the horizontal asymptote on the left side (very small values of input) for b positive, else the horizontal asymptote on the right side.
d a numeric parameter representing the horizontal asymptote on the right side (very large values of input) for b positive, else the horizontal asymptote on the left side.
x50 a numeric parameter representing the input value at the center of the curve: The value of SSrichards will be midway between a and d at x50.
x50f a numeric value, factor for x50.
X a numeric matrix with the parameters of the Richards curves.
fold a numeric with the base of the logarithm.
delta a numeric value. If abs(ny) < delta then the Gompertz curve is used.

Details

The slope (with respect to the logarithm with base fold of x) of the Richards curve is b * (d-a) * f * log(fold), with f given by ny2f.

Value

A numeric vector

Author(s)

Jens Henrik Badsberg


[Package richards version 0.5.0 Index]