plothulls {aplpack} R Documentation

## plothulls for data peeling

### Description

`plothulls plots convex hulls of a bivariate data set.`

### Usage

```plothulls(x, y, fraction, n.hull = 1, main, add = FALSE, col.hull,
lty.hull, lwd.hull, density = 0, ...)
```

### Arguments

 `x` two column matrix of the coordinates of points of x-values of a data set `y` if x is one dimensional then y contains the y-values of the data set `fraction` ... of points that lies inside the hull to be plotted `n.hull` number of directions sequential hulls to be plotted `main` title for the graphics `add` if TRUE no new plot is initialized `col.hull` color(s) of the hull(s) `lty.hull` line type(s) of the hull(s) `lwd.hull` line width(s) of the hull(s) `density` density argument of polygon() that draws the hulls `...` further arguments used in the call of plot() or points()

### Details

The function `plothulls` computes hulls of a bivariate data set using the function `chull`. After finding a hull the hull maybe plotted. Then the data points of the hull will be removed and the hull of the remaining points is computed. The style of plotting a hull depends on the setting of `col.hull`, `lty.hull`, `lwd.hull` and `density`. `density=NA` has the effect that the regions of the hulls are filled by a color. Using `fraction` you can plot a single hull. `n.hull` defines the number of hull that should be drawn one after the other.

### Value

The hull(s) are stored as a list of matrices with two columns, the innermost first and so on.

### Note

Version of plothulls: 10/2013

Peter Wolf

### References

Green, P.J. (1981): Peeling bivariate data. In: Interpreting Multivariate Data, V. Barnett (ed.), pp 3-19, Wiley. Porzio, Giovanni C., Ragozini, Giancarlo (2000): Peeling multvariate data sets: a new approach. Quanderni di Statistica, Vol. 2.

`bagplot`

### Examples

```  # 10 hulls computed from the faithful data and plotted
plothulls(faithful, n.hull=10, lty.hull=1)
# plotting additionally a hull with 90 percent of points within the hull
plot(faithful)
# hull with 10 percent of points within the hull
plothulls(faithful, fraction=.10, col.hull="red", lwd.hull=3)
# first 3 hulls of the cars data set
n <- 3
plothulls(cars, n.hull=n, col.hull=1:n, lty.hull=1:n)
# 5 hulls represented by colored regions
n <- 5
cols <- heat.colors(9)[3:(3+n-1)]
plothulls(cars, n.hull=n, col.hull=cols, lty.hull=1:n, density=NA, col=0)
points(cars, pch=17, cex=1)
# 6 hulls: regions colored and boundaries shown
n <- 6
cols <- rainbow(n)
plothulls(cars, n.hull=n, col.hull=cols, lty.hull=1:n, density=NA, col=0)
plothulls(cars, n.hull=n, add=TRUE, col.hull=1, lwd.hull=2, lty=1, col=0)
```

[Package aplpack version 1.3.5 Index]