Biexponential model
Usage
SSbiexp(input, A1, lrc1, A2, lrc2)
Arguments
input
|
a numeric vector of values at which to evaluate the model.
|
A1
|
a numeric parameter representing the multiplier of the first
exponential.
|
lrc1
|
a numeric parameter representing the natural logarithm of
the rate constant of the first exponential.
|
A2
|
a numeric parameter representing the multiplier of the second
exponential.
|
lrc2
|
a numeric parameter representing the natural logarithm of
the rate constant of the second exponential.
|
Description
This selfStart
model evaluates the biexponential model function
and its gradient. It has an initial
attribute that
will evaluate initial estimates of the parameters A1
, lrc1
,
A2
, and lrc2
for a given set of data.Value
a numeric vector of the same length as input
. It is the value of
the expression
A1*exp(-exp(lrc1)*input)+A2*exp(-exp(lrc2)*input)
.
If all of the arguments A1
, lrc1
, A2
, and
lrc2
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( Indometh )
Indo.1 <- Indometh[Indometh$Subject == 1, ]
SSbiexp( Indo.1$time, 3, 1, 0.6, -1.3 ) # response only
A1 <- 3
lrc1 <- 1
A2 <- 0.6
lrc2 <- -1.3
SSbiexp( Indo.1$time, A1, lrc1, A2, lrc2 ) # response and gradient