Outline an approximate pairwise confidence region
This function produces the ellipsoidal outline of an approximate pairwise confidence region for a nonlinear model fit.
## S3 method for class 'nls'
ellipse(x, which = c(1, 2), level = 0.95,
t = sqrt(2 * qf(level, 2, s$df[2])), ...)x |
The first argument should be an |
which |
Which selects the pair of parameters to be plotted. The default is the first two. |
level |
The confidence level of the region. Default 95%. |
t |
The t statistic on the boundary of the ellipse. |
... |
Other |
The summary function is used to obtain the approximate covariance matrix of the fitted parameters.
A matrix with columns x and y to outline the confidence region.
# Plot an approximate 95% confidence region for the weight and displacement
# parameters in the Michaelis Menten model
data(Puromycin)
fit <- nls(rate ~ Vm*conc/(K + conc), data = Puromycin, subset = state=="treated",
start = list(K = 0.05, Vm = 200))
plot(ellipse(fit,which=c('Vm','K')), type = 'l')
params <- fit$m$getPars()
points(params['Vm'],params['K'])Please choose more modern alternatives, such as Google Chrome or Mozilla Firefox.