# cell: Calculate confidence ellipses for parameters in linear models... In p3d: Plot 3d data and fitted surfaces

## Description

`cell` is similar to `confidence.ellipse` in the `car` package, except that `cell` returns the points to form the ellipse(s) which must be plotted with `plot(...,type='l')` or `lines(...)`. It currently has methods for `lm` (`cell.default`) and `glh` objects.

## Usage

 ``` 1 2 3 4 5 6 7 8 9 10 11``` ```cell(object, ...) ## Default S3 method: cell(object, which.coef, levels = 0.95, Scheffe = FALSE, dfn = 2, center.pch = 19, center.cex = 1.5, segments = 51, xlab, ylab, las = par("las"), col = palette()[2], lwd = 2, lty = 1, add = FALSE, ...) ## S3 method for class 'glh' cell(object, which.coef = 1:2, levels = 0.95, Scheffe = FALSE, dfn = 2, center.pch = 19, center.cex = 1.5, segments = 51, xlab, ylab, las = par("las"), col = palette()[2], lwd = 2, lty = 1, add = FALSE, ...) ```

## Arguments

 `object` A `lm` or `glh` object `which.coef` Indices of the coefficients, from `coef(object)` for which the confidence ellipse is to be constructed. `levels` One or more values of the confidence coverage of the ellipse(s). `Scheffe` Whether to apply Scheffe correction for dimensionality of the hypothesis `dfn` The Scheffe dimension used to calculate the radii of the ellipse(s). i.e., use `dfn = 1` to generate ellipses whose shadows are ordinary confidence intervals for individual parameters; use `dfn = 2` for 2-dimensional ellipses, etc. `center.pch` Plotting character used to mark the center of the ellipse(s) `center.cex` Size of the plotting character `segments` Number of line segments used to generate the ellipse(s) `xlab` Label for the horizontal coefficient of the plot. `ylab` Label for the vertical coefficient of the plot. `las` Style of axis labels `col` Color for the ellipse(s) `lwd` Line width for the ellipse(s) `lty` Line type for the ellipse(s) `add` This argument is not presently used `...` Other arguments passed down [where?]

## Value

Returns an object of class `ell` representing points on the boundaries of the confidence ellipse(s).

## Author(s)

Georges Monette

`ell`, for details on `ell` objects
 `1` ```# None yet ```