nlformula {lme4} | R Documentation

## Manipulate a Nonlinear Model Formula

### Description

Check and manipulate the formula for a nonlinear model, such as specified in `nlmer`.

### Usage

      nlformula(mc)

### Arguments

`mc`

matched call from the calling function, typically `nlmer()`. Should have arguments named

formula:

  a formula of the form `resp ~ nlmod ~ meform` where `resp` is an expression for the response, `nlmod` is the nonlinear model expression and `meform` is the mixed-effects model formula. `resp` can be omitted when, e.g., optimizing a design.

data:

  a data frame in which to evaluate the model function

start:

  either a numeric vector containing initial estimates for the nonlinear model parameters or a list with components

  `nlpars`:

    the initial estimates of the nonlinear model parameters

  `theta`:

    the initial estimates of the variance component parameters

### Details

The model formula for a nonlinear mixed-effects model is of the form `resp ~ nlmod ~ mixed` where `resp` is an expression (usually just a name) for the response, `nlmod` is the call to the nonlinear model function, and `mixed` is the mixed-effects formula defining the linear predictor for the parameter matrix. If the formula is to be used for optimizing designs, the `resp` part can be omitted.

### Value

a list with components

`"respMod"` | a response module of class `"nlsResp"`
`"frame"` | the model frame, including a terms attribute
`"X"` | the fixed-effects model matrix
`"reTrms"` | the random-effects terms object

### See Also

Other utilities: `findbars`, `mkRespMod`, `mkReTrms`, `nobars`, `subbars`

[Package lme4 version 1.1-11 Index]