# perspdepth: Perspective plots for depth functions In depth: Nonparametric Depth Functions for Multivariate Analysis

## Description

Draws a perspective plot of the surface of a depth function over the x-y plane.

## Usage

 ```1 2``` ```perspdepth(x, method = "Tukey", output = FALSE, tt = 50, xlab = "X", ylab = "Y", zlab = NULL, col = NULL, ...) ```

## Arguments

 `x` Bivariate data as a matrix, data frame or list. If it is a matrix or data frame, then each row is viewed as one bivariate observation. If it is a list, both components must be numerical vectors of equal length (coordinates of observations). `method` Character string which determines the depth function used. `method` can be "Tukey" (the default), "Liu" or "Oja". `output` Logical. Default FALSE produces a perspective plot; otherwise, returns a list containing the grid points and depth values over these points. `tt` Gridsize. Number of equally spaced grid points in each coordinate direction to be used in perspective plot. `xlab` Title for x-axis. Must be a character string. `ylab` Title for y-axis. Must be a character string. `zlab` Title for z-axis. Must be a character string. Default NULL identifies the depth function. `col` Color of the surface plot. Default NULL is "lightblue". `...` Any additional graphical parameters.

## Details

Requires the `rgl` package. The perspective plot takes advantage of some of the user interaction facilities of that package.

## Value

Default `output = FALSE` yields a perspective plot; otherwise the function returns a list with components

 `x` x-coordinates of the grid where the depth function is evaluated. `y` y-coordinates of the grid where the depth function is evaluated. `z` Matrix whose entry z[i ,j] is the value of the depth function at (x[i], y[j]).

## Author(s)

Jean-Claude Masse and Jean-Francois Plante, based on Fortran code by Rousseeuw, Ruts and Struyf from University of Antwerp.

## References

Rousseuw, P.J. and Ruts, I. (1996), AS 307 : Bivariate location depth, Appl. Stat.-J. Roy. S. C, 45, 516–526.

`isodepth`, `depth`
 ``` 1 2 3 4 5 6 7 8 9 10 11 12``` ```## 2 perspective plots data(geyser, package = "MASS") perspdepth(geyser, col = "magenta") set.seed(159); library(MASS) mu1 <- c(0,0); mu2 <- c(6,0); sigma <- matrix(c(1,0,0,1), nc = 2) mixbivnorm <- rbind(mvrnorm(80, mu1, sigma),mvrnorm(20, mu2, sigma)) perspdepth(mixbivnorm, col = "chartreuse") ## grid coordinates and corresponding depth values set.seed(601) x <- matrix(rnorm(48), nc = 2) perspdepth(x, output = TRUE, tt = 10) ```