hexbin: Bivariate Binning into Hexagon Cells

In hexbin: Hexagonal Binning Routines

Bivariate Binning into Hexagon Cells

Description

Creates a "hexbin" object. Basic components are a cell id and a count of points falling in each occupied cell.

Basic methods are show(), plot() and summary(), but also erode.

Usage

hexbin(x, y, xbins = 30, shape = 1,
       xbnds = range(x), ybnds = range(y),
       xlab = NULL, ylab = NULL, IDs = FALSE)

Arguments

x, y	vectors giving the coordinates of the bivariate data points to be binned. Alternatively a single plotting structure can be specified: see xy.coords. NA's are allowed and silently omitted.
xbins	the number of bins partitioning the range of xbnds.
shape	the shape = yheight/xwidth of the plotting regions.
xbnds, ybnds	horizontal and vertical limits of the binning region in x or y units respectively; must be numeric vector of length 2.
xlab, ylab	optional character strings used as labels for x and y. If NULL, sensible defaults are used.
IDs	logical indicating if the individual cell “IDs” should be returned, see also below.

Details

Returns counts for non-empty cells only. The plot shape must be maintained for hexagons to appear with equal sides. Some calculations are in single precision.

Note that when plotting a hexbin object, the grid package is used. You must use its graphics (or those from package lattice if you know how) to add to such plots.

Value

an S4 object of class "hexbin". It has the following slots:

cell	vector of cell ids that can be mapped into the (x,y) bin centers in data units.
count	vector of counts in the cells.
xcm	The x center of mass (average of x values) for the cell.
ycm	The y center of mass (average of y values) for the cell.
xbins	number of hexagons across the x axis. hexagon inner diameter =diff(xbnds)/xbins in x units
shape	plot shape which is yheight(inches) / xwidth(inches)
xbnds	x coordinate bounds for binning and plotting
ybnds	y coordinate bounds for binning and plotting
dimen	The i and j limits of cnt treated as a matrix cnt[i,j]
n	number of (non NA) (x,y) points, i.e., sum(* @count).
ncells	number of cells, i.e., length(* @count), etc
call	the function call.
xlab, ylab	character strings to be used as axis labels.
cID	of class, "integer or NULL", only if IDs was true, an integer vector of length n where cID[i] is the cell number of the i-th original point (x[i], y[i]). Consequently, the cell and count slots are the same as the names and entries of table(cID), see the example.

References

Carr, D. B. et al. (1987) Scatterplot Matrix Techniques for Large N. JASA 83, 398, 424–436.

See Also

hcell2xy gplot.hexbin, grid.hexagons, grid.hexlegend.

Examples

set.seed(101)
x <- rnorm(10000)
y <- rnorm(10000)
(bin <- hexbin(x, y))
## or
plot(hexbin(x, y + x*(x+1)/4),
     main = "(X, X(X+1)/4 + Y)  where X,Y ~ rnorm(10000)")

## Using plot method for hexbin objects:
plot(bin, style = "nested.lattice")

hbi <- hexbin(y ~ x, xbins = 80, IDs= TRUE)
str(hbi)
tI <- table(hbi@cID)
stopifnot(names(tI) == hbi@cell,
                tI  == hbi@count)

## NA's now work too:
x[runif(6, 0, length(x))] <- NA
y[runif(7, 0, length(y))] <- NA
hbN <- hexbin(x,y)
summary(hbN)

hexbin documentation built on Sept. 11, 2024, 8:58 p.m.