# ellipse.nls: Outline an approximate pairwise confidence region In ellipse: Functions for Drawing Ellipses and Ellipse-Like Confidence Regions

 ellipse.nls R Documentation

## Outline an approximate pairwise confidence region

### Description

This function produces the ellipsoidal outline of an approximate pairwise confidence region for a nonlinear model fit.

### Usage

``````## S3 method for class 'nls'
ellipse(x, which = c(1, 2), level = 0.95,
t = sqrt(2 * qf(level, 2, s\$df[2])), ...)
``````

### Arguments

 `x` The first argument should be an `nls` object, usually resulting from a call to `nls()`. `which` Which selects the pair of parameters to be plotted. The default is the first two. `level` The confidence level of the region. Default 95%. `t` The t statistic on the boundary of the ellipse. `...` Other `ellipse.default` parameters may also be used.

### Details

The summary function is used to obtain the approximate covariance matrix of the fitted parameters.

### Value

A matrix with columns `x` and `y` to outline the confidence region.

`ellipse.default`, `ellipse.profile`

### Examples

``````# Plot an approximate 95% confidence region for the weight and displacement
# parameters in the Michaelis Menten model
data(Puromycin)
fit <- nls(rate ~ Vm*conc/(K + conc), data = Puromycin, subset = state=="treated",
start = list(K = 0.05, Vm = 200))
plot(ellipse(fit,which=c('Vm','K')), type = 'l')
params <- fit\$m\$getPars()
points(params['Vm'],params['K'])
``````

ellipse documentation built on July 26, 2023, 6:10 p.m.