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

Description

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

Usage

 ```1 2 3``` ```## 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`
 ```1 2 3 4 5 6 7 8``` ```# 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']) ```