splancs (version 2.01-45)

kernrat: Ratio of two kernel smoothings

Description

Return the ratio of two kernel smoothings

Usage

kernrat(pts1,pts2,poly,h1,h2,nx=20,ny=20,kernel='quartic')

Value

A list with the following components:

x

List of x-coordinates at which the kernel function has been evaluated.

y

List of y-coordinates at which the kernel function has been evaluated.

z

A matrix of dimension nx by ny containing the ratio of the kernel functions.

h

A vector of length 2 containing h1 and h2

kernel

a character string containing the kernel name.

Arguments

pts1,pts2

Point data sets

poly

A polygon data set

h1,h2

The kernel width parameters, h1 for pts1, and h2 for pts2

nx

Number of points along the x-axis of the returned grid.

ny

Number of points along the y-axis of the returned grid.

kernel

Type of kernel function to use. Currently only the quartic kernel is implemented.

References

Berman M. and Diggle P.J. (1989) Estimating Weighted Integrals of the Second-Order Intensity of Spatial Point Patterns. J. R. Statist Soc B51 81-92; Rowlingson, B. and Diggle, P. 1993 Splancs: spatial point pattern analysis code in S-Plus. Computers and Geosciences, 19, 627-655; the original sources can be accessed at: https://www.maths.lancs.ac.uk/~rowlings/Splancs/. See also Bivand, R. and Gebhardt, A. 2000 Implementing functions for spatial statistical analysis using the R language. Journal of Geographical Systems, 2, 307-317.

See Also

kernel2d, mse2d

Examples

data(okwhite)
data(okblack)
okpoly <- list(x=c(okwhite$x, okblack$x), y=c(okwhite$y, okblack$y))
kr <- kernrat(as.points(okwhite), as.points(okblack), bboxx(bbox(as.points(okpoly))),
 h1=50, h2=50)
image(kr, asp=1)
brks <- quantile(c(kr$z), seq(0,1,1/10), na.rm=TRUE)
lbrks <- formatC(brks, 3, 6, "g", " ") 
cols <- heat.colors(length(brks)-1)
def.par <- par(no.readonly = TRUE)
layout(matrix(c(1,0,1,2), 2, 2, byrow = TRUE), c(2.5,1.5), c(1,3), TRUE)
image(kr, breaks=brks, col=cols, asp=1)
plot.new()
legend(c(0,1), c(0,1), legend=paste(lbrks[-length(lbrks)], lbrks[-1], sep=":"), fill=cols, bty="n")
par(def.par)