SSgompertz | 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
|
b3 |
a numeric parameter related to the scale the |
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
nls
, selfStart
DNase.1 <- subset(DNase, Run == 1) SSgompertz(log(DNase.1$conc), 4.5, 2.3, 0.7) # response only local({ Asym <- 4.5; b2 <- 2.3; b3 <- 0.7 SSgompertz(log(DNase.1$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) plot(density ~ log(conc), DNase.1, # xlim = c(0, 21), main = "SSgompertz() fit to DNase.1") ux <- par("usr")[1:2]; x <- seq(ux[1], ux[2], length.out=250) lines(x, do.call(SSgompertz, c(list(x=x), coef(fm1))), col = "red", lwd=2) As <- coef(fm1)[["Asym"]]; abline(v = 0, h = 0, lty = 3) axis(2, at= exp(-coef(fm1)[["b2"]]), quote(e^{-b[2]}), las=1, pos=0)
Add the following code to your website.
For more information on customizing the embed code, read Embedding Snippets.