histbackback {Hmisc} | R Documentation

## Back to Back Histograms

### Description

Takes two vectors or a list with `x` and `y` components, and produces back to back histograms of the two datasets.

### Usage

    histbackback(x, y, brks=NULL, xlab=NULL, axes=TRUE, probability=FALSE,
                 xlim=NULL, ylab='', ...)

### Arguments

`x,y` | either two vectors or a list given as `x` with two components. If the components have names, they will be used to label the axis (modification FEH).
`brks` | vector of the desired breakpoints for the histograms.
`xlab` | a vector of two character strings naming the two datasets.
`axes` | logical flag stating whether or not to label the axes.
`probability` | logical flag: if `TRUE`, then the x-axis corresponds to the units for a density. If `FALSE`, then the units are counts.
`xlim` | x-axis limits. First value must be negative, as the left histogram is placed at negative x-values. Second value must be positive, for the right histogram. To make the limits symmetric, use e.g. `ylim=c(-20,20)`.
`ylab` | label for y-axis. Default is no label.
`...` | additional graphics parameters may be given.

### Value

a list is returned invisibly with the following components:

`left` | the counts for the dataset plotted on the left.
`right` | the counts for the dataset plotted on the right.
`breaks` | the breakpoints used.

### Side Effects

a plot is produced on the current graphics device.

### Author(s)

Pat Burns
Salomon Smith Barney
London
pburns@dorado.sbi.com

### See Also

`hist`, `histogram`

### Examples

    options(digits=3)
    set.seed(1)
    histbackback(rnorm(20), rnorm(30))

    fool <- list(x=rnorm(40), y=rnorm(40))
    histbackback(fool)
    age <- rnorm(1000,50,10)
    sex <- sample(c('female','male'),1000,TRUE)
    histbackback(split(age, sex))
    agef <- age[sex=='female']; agem <- age[sex=='male']
    histbackback(list(Female=agef,Male=agem), probability=TRUE, xlim=c(-.06,.06))

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