SSChwirut: Chiwrut model for ultrasonic response
In NRAIA: Data sets from "Nonlinear Regression Analysis and Its Applications"

Description Usage Arguments Value See Also Examples

This selfStart model evaluates the Chwirut model, for an ultrasonic response. It has an initial attribute that creates initial estimates of the parameters lrc, b0 and b1. The model function also returns a "gradient" attribute.

1	SSChwirut(input, lrc, b0, b1)

`input`	a numeric vector of values at which to evaluate the model.
`lrc`	a numeric parameter representing the logarithm of the rate constant.
`b0`	a numeric parameter representing the intercept in linear denominator expression.
`b1`	a numeric parameter representing the slope in linear denominator expression.

a numeric vector of the same length as input. It is the value of the expression exp(-exp(lrc)*input)/(b0+b1*input). If all of the arguments lrc, b0 and b1 are names of objects, the gradient matrix with respect to these names is attached as an attribute named gradient.

nls, selfStart

if (require(NISTnls)) {
   coef(summary(nls(y ~ SSChwirut(x, lrc, b0, b1), Chwirut1)))
   coef(summary(nls(y ~ SSChwirut(x, lrc, b0, b1), Chwirut2)))
}