R: Method for Profiling nls Objects

profile.nls {stats} | R Documentation

## Method for Profiling nls Objects

### Description

Investigates the profile log-likelihood function for a fitted model of class `"nls"`.

### Usage

    ## S3 method for class 'nls'
    profile(fitted, which = 1:npar, maxpts = 100, alphamax = 0.01,
            delta.t = cutoff/5, ...)

### Arguments

`fitted` | the original fitted model object.
`which` | the original model parameters which should be profiled. This can be a numeric or character vector. By default, all non-linear parameters are profiled.
`maxpts` | maximum number of points to be used for profiling each parameter.
`alphamax` | highest significance level allowed for the profile t-statistics.
`delta.t` | suggested change on the scale of the profile t-statistics. Default value chosen to allow profiling at about 10 parameter values.
`...` | further arguments passed to or from other methods.

### Details

The profile t-statistics is defined as the square root of change in sum-of-squares divided by residual standard error with an appropriate sign.

### Value

A list with an element for each parameter being profiled. The elements are data-frames with two variables

`par.vals` | a matrix of parameter values for each fitted model.
`tau` | the profile t-statistics.

### Author(s)

Of the original version, Douglas M. Bates and Saikat DebRoy

### References

Bates, D. M. and Watts, D. G. (1988), Nonlinear Regression Analysis and Its Applications, Wiley (chapter 6).

### See Also

`nls`, `profile`, `plot.profile.nls`

### Examples

    # obtain the fitted object
    fm1 <- nls(demand ~ SSasympOrig(Time, A, lrc), data = BOD)
    # get the profile for the fitted model: default level is too extreme
    pr1 <- profile(fm1, alpha = 0.05)
    # profiled values for the two parameters
    pr1$A
    pr1$lrc
    # see also example(plot.profile.nls)

[Package stats version 2.15.1 Index]