erode.hexbin {hexbin} | R Documentation |

## Erosion of a Hexagon Count Image

### Description

This erosion algorithm removes counts from hexagon cells at a rate
proportional to the cells' exposed surface area. When a cell becomes
empty, algorithm removes the emptied cell and notes the removal
order. Cell removal increases the exposure of any neighboring cells.
The last cell removed is a type of bivariate median.

### Usage

erode.hexbin(bin, cdfcut = 0.5)

### Arguments

`bin` |
an object of class `hexbin` . |

`cdfcut` |
number in (0,1) indicating the confidence level for the
limits. |

### Details

The algorithm extracts high count cells with containing a given
fraction (cdfcut) of the total counts. The algorithm extracts all
cells if cdfcut=0. The algorithm performs gray-level erosion on the
extracted cells. Each erosion cycle removes counts from cells. The
counts removed for each cell are a multiple of the cell's exposed-face
count. The algorithm choses the multiple so at least one cell will be
empty or have a count deficit on each erosion cycle. The erode vector
contain an erosion number for each cell. The value of erode is

6*erosion_cycle_ at_ cell_ removal - cell_deficit_at_removal

Cells with low values are eroded first. The cell with the highest
erosion number is a candidate bivariate median. A few ties in erode
are common.

### Value

A bin object with high count cells and a component called erode that
gives the erosion order.

### See Also

`hexbin`

, `smooth.hexbin`

,
`hcell2xy`

, `hcell`

, `plot.hexbin`

,
`hboxplot`

, `hdiffplot`

,
`hmatplot`

, `hexagons`

, `hex.legend`

### Examples

set.seed(153)
x <- rnorm(10000)
y <- rnorm(10000)
bin <- hexbin(x,y)
## bivariate boxplot
smbin <- smooth.hexbin(bin)
erodebin <- erode.hexbin(smbin,cdfcut=.5)
hboxplot(erodebin)
# show erosion order
oldpar <- par(no.readonly=TRUE)
screenpar <- plot.hexbin(bin,style= "lat", minarea=1, maxarea=1,
legend=FALSE, border=gray(.7))
par(screenpar) # reset to the plot on the screen
hexagons(erodebin,style= "lat", minarea=1, maxarea=1,pen="green")
xy <- hcell2xy(erodebin)
text(xy, lab = as.character(erodebin$erode),col="white",cex=.65)
par(oldpar)

[Package

*hexbin* version 1.0.10

Index]