Description Usage Arguments Details Value Author(s) References See Also Examples

Constructs and optionally plots a set of probability ellipses for a bivariate normal distribution with defined centre and covariance.

1 2 3 4 5 6 7 |

`cov` |
Covariance and location object of class |

`probs` |
A vector of probabilities at which ellipses will be constructed. |

`plot` |
Logical specifying whether the ellipses constructed will additionally be plotted.
If |

`npoints` |
Integer number of points for each quadrant of the ellipses returned. |

`object` |
Object of class |

`x` |
Object of class |

`...` |
Arguments passed to other methods, particularly |

`data.ellipse`

constructs and returns one set of x, y coordinates for each value of
`probs`

, in a form that can be passed directly to `polygon`

.

Ellipses are constructed from the upper `probs`

quantile of the F distribution using

`T = sqrt( 2 * (n - 1) * qf(probs, 2, n - 1)/(n - 2))`

where `n`

is the number of pairs used in forming the covariance matrix.
If the number of points is missing or NA, `Inf`

is substituted.

Summary and print methods are provided. The summary method returns a list with the
same names as class `d.ellipse`

, each containing a default summary of the respective
member of the `d.ellipse`

object. The print method returns its argument invisibly.

An object of class `d.ellipse`

, consisting of:

`ellipses` |
A named list of ellipsoids named for each probability in |

`probs` |
Numeric vector of probabilities as supplied by |

`cov` |
Covariance object of class |

S L R Ellison

ISO 13528:2005 Statistical methods for use in proficiency testing by interlaboratory comparisons. (2005) International organization for Standardizaton, Geneva

Jackson, J. E. (1956) *Quality control methods for two related variables*.
Industrial Quality Control, Vol. 7, pp. 2-6

Jackson, J. E. (1959) *Control Methods for Several Related Variables*.
Technometrics, Vol. 1, pp. 359-377

`cov.dellipse`

, `plot.d.ellipse`

, `polygon`

1 2 3 4 | ```
data(chromium)
cov.Cr <- cov.dellipse(chromium)
dellipse.Cr <- data.ellipse(cov.Cr, plot=FALSE)
summary(dellipse.Cr)
``` |

```
Attaching package: 'metRology'
The following objects are masked from 'package:base':
cbind, rbind
$ellipses
Length Class Mode
p=0.95 396 -none- numeric
$probs
Min. 1st Qu. Median Mean 3rd Qu. Max.
0.95 0.95 0.95 0.95 0.95 0.95
$cov
Length Class Mode
method 1 -none- character
cov 4 -none- numeric
cor 4 -none- numeric
center 2 -none- numeric
scale 2 -none- numeric
n.obs 1 -none- numeric
```

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