SSgompertz {stats} | R Documentation |
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
.
SSgompertz(x, Asym, b2, b3)
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. |
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
.
Douglas Bates
DNase.1 <- subset(DNase, Run == 1) SSlogis(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 getInitial(density ~ SSgompertz(log(conc), Asym, b2, b3), data = DNase.1) ## Initial values are in fact the converged values fm1 <- nls(density ~ SSgompertz(log(conc), Asym, b2, b3), data = DNase.1) summary(fm1)