SSallometric {FAwR}

Self-starting version of the allometric function y = a x^b.

Description

This function is used for fitting the allometric function to bivaraite data. The function is of the form y = alpha x ^ beta, where traditionally x and y are different dimensions of a sampling unit, such as diameter and volume of a tree.

Usage

SSallometric(x, alpha, beta)

Arguments

x

predictor variable (e.g. volume)

alpha

product parameter

beta

exponent parameter

Value

The function returns a numeric vector of response variables. The vector has two additional attributes: the gradient, which reports the first derivative of the function with respect to the parameters, evaluated at the response value; and the hessian, which reports the matrix of second partial derivatives of the function with respect to the parameters evaluated at the response variable.

Note

Demonstrates construction and usage of self-starting functions using selfStart.

Author(s)

Andrew Robinson <[e-mail]>

References

Robinson, A.P., and J.D. Hamann. 2010. Forest Analytics with R: an Introduction. Springer.

See Also

selfStart

Examples

SSallometric(10, 2, 3)

data(sweetgum)
nls(vol.m3 ~ SSallometric(dbh.cm, alpha, beta),  data = sweetgum)