# sectioned.density: Sectioned density plots In denstrip: Density Strips and Other Methods for Compactly Illustrating Distributions

## Description

Sectioned density plots (Cohen and Cohen, 2006) use shading and occlusion to give a compact illustration of a distribution, such as the empirical distribution of data.

## Usage

 ```1 2 3 4 5``` ```sectioned.density(x, dens, at, width, offset, ny, method=c("kernel","frequency"), nx, horiz=TRUE, up.left = TRUE, colmax, colmin="white", gamma=1, lattice=FALSE, ...) panel.sectioned.density(...) ```

## Arguments

 `x` Either the vector of points at which the density is evaluated (if `dens` supplied), or a sample from the distribution (if `dens` not supplied). `dens` Density at `points`. If `dens` is not supplied, the density of the distribution underlying `x` is estimated using the method specified in `method`. `at` Position of the bottom of the plot on the y-axis (if `horiz=TRUE`) or position of the right of the plot on the x-axis (if `horiz=FALSE`) (required). `ny` Number of fixed-width intervals for categorising the density. `width` Width of individual rectangles in the plot. Defaults to the range of the axis divided by 20. `offset` Offset for adjacent rectangles. Defaults to `width/3`. `method` Method of estimating the density of `x`, when `dens` is not supplied. If `"kernel"` (the default) then kernel density estimation is used, via `density(x,...)`. If `"frequency"` then the density is estimated as the relative frequency in a series of bins, as in Cohen and Cohen (2006). This method is controlled by the number of data bins `nx`. `nx` Number of data bins for the `"frequency"` density estimation method. The default uses Sturges' formula (see `nclass.Sturges`, `hist`). `horiz` If `horiz=TRUE`, then the plot is horizontal and points upwards. If `horiz=FALSE` then the plot is vertical and points leftwards, as the illustrations in Cohen and Cohen (2006). `up.left` If changed to `FALSE`, then horizontal plots point downwards and vertical plots point rightwards. `colmax` Darkest colour, either as a built-in R colour name (one of `colors()`) or an RGB hex value. Defaults to `par("fg")` or its lattice equivalent, which is normally `"black"`, or `"#000000"`. `colmin` Lightest colour, either as a built-in R colour name (one of `colors()`) or an RGB hex value. Defaults to white. `gamma` Gamma correction to apply to the colour palette, see `denstrip`. `lattice` Set this to `TRUE` to make `sectioned.density` a lattice panel function instead of a base graphics function. `panel.sectioned.density(x,...)` is equivalent to `sectioned.density(x, lattice=TRUE, ...)`. `...` Additional arguments supplied to `density(x,...)`, if `method="kernel"`.

## Author(s)

Christopher Jackson <[email protected]> (R implementation)

## References

Cohen, D. J. and Cohen, J. The sectioned density plot. The American Statistician (2006) 60(2):167–174

## Examples

 ``` 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25``` ```## Fisher's iris data ## Various settings to change the look of the plot hist(iris\$Sepal.Length, nclass=20, col="lightgray") sectioned.density(iris\$Sepal.Length, at=0.2) sectioned.density(iris\$Sepal.Length, at=5) sectioned.density(iris\$Sepal.Length, at=10, width=0.5) hist(iris\$Sepal.Length, nclass=20, col="lightgray") sectioned.density(iris\$Sepal.Length, at=7, width=0.5, offset=0.1, colmax="darkmagenta") sectioned.density(iris\$Sepal.Length, at=9, width=0.5, offset=0.1, ny=15, colmin="lemonchiffon") ## frequency method less smooth than kernel density sectioned.density(iris\$Sepal.Length, at=12, width=0.5, offset=0.1, method="frequency") sectioned.density(iris\$Sepal.Length, at=13.5, width=0.5, offset=0.1, method="frequency", nx=20) ## Illustrate a known distribution x <- seq(-4, 4, length=1000) dens <- dnorm(x) plot(x, xlim=c(-5, 5), ylim=c(-5, 5), xlab="x", ylab="x", type="n") sectioned.density(x, dens, ny=8, at=0, width=0.3) sectioned.density(x, dens, ny=16, at=2, width=0.1) sectioned.density(x, dens, at=-3, horiz=FALSE) sectioned.density(x, dens, at=4, width=0.3, horiz=FALSE) ```

denstrip documentation built on March 18, 2018, 5:31 p.m.