Hexagon Coordinates and Polygon Drawing

Simple ‘low-level’ function for computing and drawing hexagons. Can be used for ‘grid’ (package grid) or ‘traditional’ (package graphics) graphics.

hexcoords(dx, dy = NULL, n = 1, sep = NULL)

hexpolygon(x, y, hexC = hexcoords(dx, dy, n = 1), dx, dy = NULL,
           fill = 1, border = 0, hUnit = "native", ...)

Arguments

dx,dy

horizontal and vertical width of the hexagon(s).

n

number of hexagon “repeats”.

sep

separator value to be put between coordinates of different hexagons. The default, NULL doesn't use a separator.

x,y

numeric vectors of the same length specifying the hexagon centers around which to draw.

hexC

a list as returned from hexcoords(). Its component no.sep determines if grid or traditional graphics are used. The default (via default of hexcoords) is now to use grid graphics.

fill,border

passed to grid.polygon (for grid).

hUnit

string or NULL determining in which units (x,y) values are.

...

further arguments passed to polygon (for graphics).

Value

hexcoords() returns a list with components

x,y

numeric vectors of length \(n \times 6\) (or \(n \times 7\) if sep is not NULL) specifying the hexagon polygon coordinates (with sep appended to each 6-tuple).

no.sep

a logical indicating if sep was NULL.

hexpolygon returns what its last grid.polygon(.)

or polygon(.) call returns.

Author

Martin Maechler, originally.

See also

grid.hexagons which builds on these.

Examples

str(hexcoords(1, sep = NA))  # multiple of (6 + 1)
#> List of 3
#>  $ x     : num [1:7] 1 1 0 -1 -1 0 NA
#>  $ y     : num [1:7] 0.577 -0.577 -1.155 -0.577 0.577 ...
#>  $ no.sep: logi FALSE
str(hexcoords(1, sep = NULL))# no separator -> multiple of 6
#> List of 3
#>  $ x     : num [1:6] 1 1 0 -1 -1 0
#>  $ y     : num [1:6] 0.577 -0.577 -1.155 -0.577 0.577 ...
#>  $ no.sep: logi TRUE
# \dontshow{
stopifnot(3 * (6+1) == sapply(hexcoords(2, n = 3, sep = NA)[1:2], length),
          6 == sapply(hexcoords(1)[1:2], length))
set.seed(1001)
# }

## hexpolygon()s:
x <- runif(20, -2, 2)
y <- x + rnorm(20)

## 1) traditional 'graphics'
plot(x,y, asp = 1, "plot() + hexpolygon()")
#> Warning: plot type 'plot() + hexpolygon()' will be truncated to first character
hexpolygon(x,y, dx = 0.1, density = 25, col = 2, lwd = 1.5)


## 2) "grid" :

addBit <- function(bnds, f = 0.05) bnds + c(-f, f) * diff(bnds)
sc <- addBit(rxy <- range(x,y))# same extents (cheating asp=1)
library("grid")
grid.newpage()
pushViewport(plotViewport(.1+c(4,4,2,1), xscale = sc, yscale = sc))
grid.rect()
grid.xaxis()
grid.yaxis()
grid.points(x,y)
hexpolygon(x,y, hexcoords(dx = 0.1, sep=NULL), border = "blue", fill=NA)
popViewport()