# myplotDD: Distance-Distance Plot In robustfa: An Object Oriented Solution for Robust Factor Analysis

## Description

`"myplotDD"` is a revised version of `".myddplot"` in `"plot-utils.R"` in the package `"rrcov"`. In `"myplotDD"`, `id.n` and `ind` are printed out.

## Usage

 `1` ```myplotDD(x, cutoff, id.n) ```

## Arguments

 `x` An S4 object of class `"CovRobust"`. `cutoff` The `cutoff` value used. If missing, `cutoff <- sqrt(qchisq(0.975, p))` by default. `id.n` Number of observations to identify by a label. If not supplied, the number of observations with robust distance larger than `cutoff` is used.

## Details

Distance-Distance Plot: Plot the vector `y=rd` (robust distances) against `x=md` (mahalanobis distances). Identify by a label the `id.n` observations with largest `rd`. If `id.n` is not supplied, calculate it as the number of observations larger than `cutoff`. Use `cutoff` to draw a horisontal and a vertical line. Draw also a dotted line with a slope 1.

`"myplotDD(x)"` is equivalent to `"plot(x, which="dd")"`. `which`: indicate what kind of plot. If `which = "dd"`, then a distance-distance Plot.

## Value

A distance-distance plot is shown. Return a list with components:

 `cutoff ` The `cutoff` value used. If missing, `cutoff <- sqrt(qchisq(0.975, p))` by default. `id.n ` Number of observations to identify by a label. If not supplied, the number of observations with robust distance larger than `cutoff` is used. `sort.y ` A list containing the sorted values of y (the robust distance) `ind ` The indices of the largest `id.n` observations whose robust distances are larger than `cutoff`.

## Author(s)

Ying-Ying Zhang (Robert) [email protected]

## References

Zhang, Y. Y. (2013), An Object Oriented Solution for Robust Factor Analysis.

`plot`, `qchisq`, `CovClassic`, `getDistance`
 ``` 1 2 3 4 5 6 7 8 9 10``` ```data(stock611) covMcd=CovRobust(x=scale(stock611[,3:12]), control="mcd"); covMcd ## "myplotDD" shows id.n and ind. ## Note: id.n and ind change each time due to covMcd changes each time! ## However, the ind of largest robust distances do not change. result = myplotDD(x=covMcd); result ## "myplotDD" is equivalent to "plot(x=covMcd, which="dd")". plot(x=covMcd, which="dd") ```