FAwR (version 1.2.0)

SSallometric: 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)

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.

Arguments

x

predictor variable (e.g. volume)

alpha

product parameter

beta

exponent parameter

Author

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)