grid.hexagons

From hexbin v1.29.0 by Nicholas LewinKoh

Add Hexagon Cells to Plot

Plots cells in an hexbin object. The function distinquishes among counts using 5 different styles. This function is the hexagon plotting engine from the plot method for hexbin objects.

Keywords: aplot

Usage

grid.hexagons(dat, style = c("colorscale", "centroids", "lattice",
	      "nested.lattice", "nested.centroids", "constant.col"),
         use.count=TRUE, cell.at=NULL,
	 minarea = 0.05, maxarea = 0.8, check.erosion = TRUE,
	 mincnt = 1, maxcnt = max(dat@count), trans = NULL,
	 colorcut = seq(0, 1, length = 17),
	 density = NULL, border = NULL, pen = NULL,
	 colramp = function(n){ LinGray(n,beg = 90, end = 15) },
	 def.unit=  "native",
	 verbose = getOption("verbose"))

Arguments

dat: an object of class hexbin, see hexbin.
style: character string specifying the type of plotting; must be (a unique abbrevation) of the values given in Usage above.
use.count: logical specifying if counts should be used.
cell.at: numeric vector to be plotted instead of counts, must besame length as the number of cells.
minarea: numeric, the fraction of cell area for the lowest count.
maxarea: the fraction of the cell area for the largest count.
check.erosion: logical indicating only eroded points should be used for "erodebin" objects; simply passed to hcell2xy, see its documentation.
mincnt: numeric; cells with counts smaller than mincnt are not shown.
maxcnt: cells with counts larger than this are not shown.
trans: a transformation function (or NULL) for the counts, e.g., sqrt.
colorcut: a vector of values covering [0, 1] which determine hexagon color class boundaries or hexagon size boundaries -- for style = "colorscale" only.
density: grid.polygon argument for shading. 0 causes the polygon not to be filled. This is not implemented (for grid.polygon) yet.
border: grid.polygon() argument. Draw the border for each hexagon.
pen: colors for grid.polygon(). Determines the color with which the polygon will be filled.
colramp: function of an integer argument n returning n colors. n is determined
def.unit: default unit to be used.
verbose: logical indicating if some diagnostic output should happen.

Details

The six plotting styles have the following effect: [object Object],[object Object],[object Object],[object Object]

Hexagon size encoding minarea and maxarea determine the area of the smallest and largest hexagons plotted. Both are expressed fractions of the bin cell size. Typical values might be .04 and 1. When both values are 1, all plotted hexagons are bin cell size, if maxarea is greater than 1 than hexagons will overlap. This is sometimes interesting with the lattice and centroid styles.

Count scaling

relcnt <- (trans(cnt)-trans(mincnt)) / (trans(maxcnt)-trans(mincnt)) area <- minarea + relcnt*maxarea

By default the transformation trans() is the identity function. The legend routine requires the transformation inverse for some options.

Count windowing mincnt and maxcnt Only routine only plots cells with cnts in [mincnts, maxcnts]

SIDE EFFECTS

Adds hexagons to the plot.

References

Carr, D. B. (1991) Looking at Large Data Sets Using Binned Data Plots, pp. 7--39 in Computing and Graphics in Statistics; Eds. A. Buja and P. Tukey, Springer-Verlag, New York.

Examples

set.seed(506)
x <- rnorm(10000)
y <- rnorm(10000)

# bin the points
bin <- hexbin(x,y)

# Typical approach uses plot( <hexbin> ) which controls the plot shape :
plot(bin, main = "Bivariate rnorm(10000)")

## but we can have more manual control:

# A mixture distribution
x <- c(rnorm(5000),rnorm(5000,4,1.5))
y <- c(rnorm(5000),rnorm(5000,2,3))
hb2 <- hexbin(x,y)

# Show color control and overplotting of hexagons
## 1) setup coordinate system:
P <- plot(hb2, type="n", main = "Bivariate mixture (10000)")# asp=1

## 2) add hexagons (in the proper viewport):
pushHexport(P$plot.vp)
grid.hexagons(hb2, style= "lattice", border = gray(.1), pen = gray(.6),
              minarea = .1, maxarea = 1.5)
popViewport()

## How to treat 'singletons' specially:
P <- plot(hb2, type="n", main = "Bivariate mixture (10000)")# asp=1
pushHexport(P$plot.vp)
grid.hexagons(hb2, style= "nested.centroids", mincnt = 2)# not the single ones
grid.hexagons(hb2, style= "centroids", maxcnt = 1, maxarea=0.04)# single points
popViewport()

Documentation reproduced from package hexbin, version 1.29.0, License: GPL-2

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