fitModel: Fit a nonlinear least squares model

In mosaic: Project MOSAIC Statistics and Mathematics Teaching Utilities

Fit a nonlinear least squares model

Description

Allows you to specify a formula with parameters, along with starting guesses for the parameters. Refines those guesses to find the least-squares fit.

Usage

fitModel(formula, data = parent.frame(), start = list(), ...)

model(object, ...)

## S3 method for class 'nlsfunction'
model(object, ...)

## S3 method for class 'nlsfunction'
summary(object, ...)

## S3 method for class 'nlsfunction'
coef(object, ...)

Arguments

formula	formula specifying the model
data	dataframe containing the data to be used
start	passed as start to nls(). If and empty list, a simple starting point is used (thus avoiding the usual warning message).
...	additional arguments passed to nls()
object	an R object (typically a the result of fitModel)

Details

Fits a nonlinear least squares model to data. In contrast to linear models, all the parameters (including linear ones) need to be named in the formula. The function returned simply contains the formula together with pre-assigned arguments setting the parameter value. Variables used in the fitting (as opposed to parameters) are unassigned arguments to the returned function.

Value

a function

Note

This doesn't work with categorical explanatory variables. Also, this does not work with synthetic data that fit the model perfectly. See link{nls} for details.

See Also

linearModel(), nls()

Examples

if (require(mosaicData)) {
f <- fitModel(temp ~ A+B*exp(-k*time), data=CoolingWater, start=list(A=50,B=50,k=1/20))
f(time=50)
coef(f)
summary(f)
model(f)
}

mosaic documentation built on Nov. 10, 2023, 1:11 a.m.