getInitial                package:nls                R Documentation

Get Initial Parameter Estimates

Description:

     This function evaluates initial parameter estimates for a
     nonlinear regression model.  If `data' is a parameterized data
     frame or `pframe' object, its `parameters' attribute is returned.
     Otherwise the object is examined to see if it contains a call to a
     `selfStart' object whose `initial' attribute can be evaluated.

Usage:

     getInitial(object, data, ...)

Arguments:

  object: a formula or a `selfStart' model that defines a nonlinear
          regression model

    data: a data frame in which the expressions in the formula or
          arguments to the `selfStart' model can be evaluated

     ...: optional additional arguments

Value:

     A named numeric vector or list of starting estimates for the
     parameters.  The construction of many `selfStart' models is such
     that these "starting" estimates are, in fact, the converged
     parameter estimates.

Author(s):

     Jose Pinheiro and Douglas Bates

See Also:

     `nls',  `selfStart', `selfStart.default', `selfStart.formula'

Examples:

     data(Puromycin)
     PurTrt <- Puromycin[ Puromycin$state == "treated", ]
     getInitial( rate ~ SSmicmen( conc, Vm, K ), PurTrt )

