hexContour: Generate contour for a hexagonal grid.

In hexDensity: Fast Kernel Density Estimation with Hexagonal Grid

Generate contour for a hexagonal grid.

Description

Algorithm is a modification of the meandering triangles as described in https://blog.bruce-hill.com/meandering-triangles to work with hexagons. See isolines for details about the output.

Usage

hexContour(hexDensity, levels)

Arguments

hexDensity	hexDensity object to be contoured.
levels	Numeric vector for which contour lines should be generated

Details

This function is made to follow the same behaviour as isolines. A dedicated plotting function is in the work. Meanwhile, see example of how to plot the output with ggplot2's geom_path.

Value

A list of x, y, and ID, for the contour line at each levels. ID indicates the different line segments making up the contour.

Examples

set.seed(133)
x=rnorm(200)
y=rnorm(200)
d = hexDensity(x=x,y=y,bandwidth=0.4)
cutoff=quantile(d@count,0.9)
lines = hexContour(d,cutoff)

library(ggplot2)
library(hexbin)
#plot against density
ggplot()+
  geom_point(
    aes(x=hcell2xy(d)$x,
        y=hcell2xy(d)$y,
        col=d@count)
 ) +
  scale_color_viridis_c()+
  geom_path(
    aes(
     x = lines[[1]]$x, y = lines[[1]]$y, group = lines[[1]]$id
    )
  )

#plot against data points
ggplot() +
  geom_point(
    aes(x=x,y=y)) +
  geom_path(
    aes(
      x = lines[[1]]$x, y = lines[[1]]$y, group = lines[[1]]$id
    )
  )

hexDensity documentation built on June 8, 2025, 1:10 p.m.