SSgompertz
SelfStarting Nls Gompertz Growth Model
This selfStart
model evaluates the Gompertz growth model
and its gradient. It has an initial
attribute that
creates initial estimates of the parameters Asym
,
b2
, and b3
.
 Keywords
 models
Usage
SSgompertz(x, Asym, b2, b3)
Arguments
 x
 a numeric vector of values at which to evaluate the model.
 Asym
 a numeric parameter representing the asymptote.
 b2
 a numeric parameter related to the value of the function at
x = 0
 b3
 a numeric parameter related to the scale the
x
axis.
Value

a numeric vector of the same length as
input
. It is the value of
the expression Asym*exp(b2*b3^x)
. If all of
the arguments Asym
, b2
, and b3
are
names of objects the gradient matrix with respect to these names is attached as
an attribute named gradient
.
See Also
Examples
library(stats)
DNase.1 < subset(DNase, Run == 1)
SSgompertz(log(DNase.1$conc), 4.5, 2.3, 0.7) # response only
Asym < 4.5; b2 < 2.3; b3 < 0.7
SSgompertz(log(DNase.1$conc), Asym, b2, b3) # response and gradient
print(getInitial(density ~ SSgompertz(log(conc), Asym, b2, b3),
data = DNase.1), digits = 5)
## Initial values are in fact the converged values
fm1 < nls(density ~ SSgompertz(log(conc), Asym, b2, b3),
data = DNase.1)
summary(fm1)
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