akde2d: Two-Dimensional Kernel Density Estimation (Astro)
Description
Two-dimensional kernel density estimation with an axis-aligned bivariate normal kernel, evaluated on a square grid. The function 'akde2d' (astro:kde2d) is a wrapper around the 'kde2d' function within the 'MASS' package. This function adds additional output to that function.
Usage
akde2d(x, y, n = 25, lims = c(range(x), range(y)), levels = seq(0,0.9,by=0.1), ...)
Arguments
x
x coordinate of data
y
y coordinate of data
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)'
levels
output levels containing the given percentiles of the data
...
arguments to be passed to 'kde2d' in the 'MASS' package
Value
A list of four 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'
l
percentile levels containing given fractions of the data
Details
Characters in the string will be stripped 'outside in', from left-to-right in the order they are given in the argument. See examples below for more detail.
References
Venables, W. N. and Ripley, B. D. (2002) _Modern Applied Statistics with S._ Fourth edition. Springer.