# ConfRadius: Helper to compute confidence ellipsoids In compositions: Compositional Data Analysis

## Description

Computes the quantile of the Mahalanobis distance needed to draw confidence ellipsoids.

## Usage

 ```1 2``` ```ConfRadius(model,prob=1-alpha,alpha) ```

## Arguments

 `model` A multivariate linear model `prob` The confidence probability `alpha` The alpha error allowed, i.e. the complement of the confidence probability

## Details

Calculates the radius to be used in confidence ellipses for the parameters based on the Hottelings T^2 distribution.

a scalar

## Author(s)

K.Gerald v.d. Boogaart http://www.stat.boogaart.de

`lm`, `mvar`, `AIC`

## Examples

 ```1 2 3 4 5 6 7 8 9``` ```data(SimulatedAmounts) model <- lm(ilr(sa.groups)~sa.groups.area) cf = coef(model) plot(ilrInv(cf, x=sa.groups)) for(i in 1:nrow(cf)){ vr = vcovAcomp(model)[,,i,i] vr = ilrvar2clr(vr) ellipses(ilrInv(cf[i,]), vr, r=ConfRadius(model, alpha=0.05) ) } ```

### Example output

```Loading required package: tensorA

Attaching package: 'tensorA'

The following object is masked from 'package:base':

norm

Welcome to compositions, a package for compositional data analysis.
Find an intro with "? compositions"

Attaching package: 'compositions'

The following objects are masked from 'package:stats':

cor, cov, dist, var

The following objects are masked from 'package:base':

%*%, scale, scale.default

Warning messages:
1: In structure(c(), class = c(class(x), class(y))) :
Calling 'structure(NULL, *)' is deprecated, as NULL cannot have attributes.
2: In structure(c(), class = c(class(x), class(y))) :
Calling 'structure(NULL, *)' is deprecated, as NULL cannot have attributes.
3: In structure(c(), class = c(class(x), class(y))) :
Calling 'structure(NULL, *)' is deprecated, as NULL cannot have attributes.
4: In structure(c(), class = c(class(x), class(y))) :
Calling 'structure(NULL, *)' is deprecated, as NULL cannot have attributes.
5: In structure(c(), class = c(class(x), class(y))) :
Calling 'structure(NULL, *)' is deprecated, as NULL cannot have attributes.
Warning messages:
1: In structure(c(), class = c(class(x), class(y))) :
Calling 'structure(NULL, *)' is deprecated, as NULL cannot have attributes.
2: In structure(c(), class = c(class(x), class(y))) :
Calling 'structure(NULL, *)' is deprecated, as NULL cannot have attributes.
3: In structure(c(), class = c(class(x), class(y))) :
Calling 'structure(NULL, *)' is deprecated, as NULL cannot have attributes.
4: In structure(c(), class = c(class(x), class(y))) :
Calling 'structure(NULL, *)' is deprecated, as NULL cannot have attributes.
5: In structure(c(), class = c(class(x), class(y))) :
Calling 'structure(NULL, *)' is deprecated, as NULL cannot have attributes.
6: In structure(c(), class = c(class(x), class(y))) :
Calling 'structure(NULL, *)' is deprecated, as NULL cannot have attributes.
7: In structure(c(), class = c(class(x), class(y))) :
Calling 'structure(NULL, *)' is deprecated, as NULL cannot have attributes.
8: In structure(c(), class = c(class(x), class(y))) :
Calling 'structure(NULL, *)' is deprecated, as NULL cannot have attributes.