hexbin (version 1.29.0)

hexbin: 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.

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.

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.

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)