# kde2d {MASS}

### Description

Two-dimensional kernel density estimation with an axis-aligned bivariate normal kernel, evaluated on a square grid.

### Usage

kde2d(x, y, h, n = 25, lims = c(range(x), range(y)))

### Arguments

- x
- x coordinate of data
- y
- y coordinate of data
- h
- vector of bandwidths for x and y directions. Defaults to normal reference bandwidth (see
`bandwidth.nrd`

). A scalar value will be taken to apply to both directions. - n
- Number of grid points in each direction. Can be scalar or a length-2 integer vector.
- lims
- The limits of the rectangle covered by the grid as
`c(xl, xu, yl, yu)`

.

### Values

A list of three components.

- x, y
- The x and y coordinates of the grid points, vectors of length
`n`

. - z
- An
`n[1]`

by`n[2]`

matrix of the estimated density: rows correspond to the value of`x`

, columns to the value of`y`

.

### References

Venables, W. N. and Ripley, B. D. (2002) *Modern Applied Statistics with S.* Fourth edition. Springer.

### Examples

attach(geyser) plot(duration, waiting, xlim = c(0.5,6), ylim = c(40,100)) f1 <- kde2d(duration, waiting, n = 50, lims = c(0.5, 6, 40, 100)) image(f1, zlim = c(0, 0.05)) f2 <- kde2d(duration, waiting, n = 50, lims = c(0.5, 6, 40, 100), h = c(width.SJ(duration), width.SJ(waiting)) ) image(f2, zlim = c(0, 0.05)) persp(f2, phi = 30, theta = 20, d = 5) plot(duration[-272], duration[-1], xlim = c(0.5, 6), ylim = c(1, 6),xlab = "previous duration", ylab = "duration") f1 <- kde2d(duration[-272], duration[-1], h = rep(1.5, 2), n = 50, lims = c(0.5, 6, 0.5, 6)) contour(f1, xlab = "previous duration", ylab = "duration", levels = c(0.05, 0.1, 0.2, 0.4) ) f1 <- kde2d(duration[-272], duration[-1], h = rep(0.6, 2), n = 50, lims = c(0.5, 6, 0.5, 6)) contour(f1, xlab = "previous duration", ylab = "duration", levels = c(0.05, 0.1, 0.2, 0.4) ) f1 <- kde2d(duration[-272], duration[-1], h = rep(0.4, 2), n = 50, lims = c(0.5, 6, 0.5, 6)) contour(f1, xlab = "previous duration", ylab = "duration", levels = c(0.05, 0.1, 0.2, 0.4) ) detach("geyser")

Documentation reproduced from package MASS, version 7.3-45. License: GPL-2 | GPL-3