Asymptotic Regression Model

Usage

SSasymp(input, Asym, R0, lrc)

Arguments

input a numeric vector of values at which to evaluate the model.
Asym a numeric parameter representing the horizontal asymptote on the right side (very large values of input).
R0 a numeric parameter representing the response when input is zero.
lrc a numeric parameter representing the natural logarithm of the rate constant.

Description

This selfStart model evaluates the asymptotic regression function and its gradient. It has an initial attribute that will evaluate initial estimates of the parameters Asym, R0, and lrc for a given set of data.

Value

a numeric vector of the same length as input. It is the value of the expression Asym+(R0-Asym)*exp(-exp(lrc)*input). If all of the arguments Asym, R0, and lrc are names of objects, as opposed to expressions or explicit numerical values, the gradient matrix with respect to these names is attached as an attribute named gradient.

Author(s)

Jose Pinheiro and Douglas Bates

See Also

nls, selfStart

Examples

library( lme )
data( Loblolly )
Lob.329 <- Loblolly[ Loblolly$Seed == "329", ]
SSasymp( Lob.329$age, 100, -8.5, -3.2 )  # response only
Asym <- 100
resp0 <- -8.5
lrc <- -3.2
SSasymp( Lob.329$age, Asym, resp0, lrc ) # response and gradient


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