Alternative Asymptotic Regression Model with an Offset
Usage
SSasympOff(input, Asym, lrc, c0)
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 ).
|
lrc
|
a numeric parameter representing the natural logarithm of
the rate constant.
|
c0
|
a numeric parameter representing the input when
response is zero.
|
Description
This selfStart
model evaluates the alternative asymptotic
regression function and its gradient. It has an initial
attribute that will evaluate initial estimates of the parameters
Asym
, lrc
, and c0
for a given set of data.Value
a numeric vector of the same length as input
. It is the value of
the expression Asym*(1 - exp(-exp(lrc)*(input - c0)))
. If all of
the arguments Asym
, lrc
, and c0
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 BatesSee Also
nls
, selfStart
Examples
library( lme )
data( CO2 )
CO2.Qn1 <- CO2[CO2$Plant == "Qn1", ]
SSasympOff( CO2.Qn1$conc, 32, -4, 43 ) # response only
Asym <- 32
lrc <- -4
c0 <- 43
SSasympOff( CO2.Qn1$conc, Asym, lrc, c0 ) # response and gradient