Draw Histograms and Kernel Density Plots, possibly conditioned on other variables.

```
histogram(x, data, …)
densityplot(x, data, …)
# S3 method for formula
histogram(x,
data,
allow.multiple, outer = TRUE,
auto.key = FALSE,
aspect = "fill",
panel = lattice.getOption("panel.histogram"),
prepanel, scales, strip, groups,
xlab, xlim, ylab, ylim,
type = c("percent", "count", "density"),
nint = if (is.factor(x)) nlevels(x)
else round(log2(length(x)) + 1),
endpoints = extend.limits(range(as.numeric(x),
finite = TRUE), prop = 0.04),
breaks,
equal.widths = TRUE,
drop.unused.levels =
lattice.getOption("drop.unused.levels"),
…,
lattice.options = NULL,
default.scales = list(),
default.prepanel =
lattice.getOption("prepanel.default.histogram"),
subscripts,
subset)
```# S3 method for numeric
histogram(x, data = NULL, xlab, …)
# S3 method for factor
histogram(x, data = NULL, xlab, …)

# S3 method for formula
densityplot(x,
data,
allow.multiple = is.null(groups) || outer,
outer = !is.null(groups),
auto.key = FALSE,
aspect = "fill",
panel = lattice.getOption("panel.densityplot"),
prepanel, scales, strip, groups, weights,
xlab, xlim, ylab, ylim,
bw, adjust, kernel, window, width, give.Rkern,
n = 512, from, to, cut, na.rm,
drop.unused.levels =
lattice.getOption("drop.unused.levels"),
…,
lattice.options = NULL,
default.scales = list(),
default.prepanel =
lattice.getOption("prepanel.default.densityplot"),
subscripts,
subset)
# S3 method for numeric
densityplot(x, data = NULL, xlab, …)

do.breaks(endpoints, nint)

x

The object on which method dispatch is carried out.

For the `formula`

method, `x`

can be a formula of the form
`~ x | g1 * g2 * …`

, indicating that histograms or kernel
density estimates of the `x`

variable should be produced
conditioned on the levels of the (optional) variables `g1`

,
`g2`

, …. `x`

should be numeric (or possibly a factor
in the case of `histogram`

), and each of `g1`

, `g2`

,
… should be either factors or shingles.

As a special case, the right hand side of the formula can contain
more than one term separated by ‘+’ signs (e.g., ```
~ x1 +
x2 | g1 * g2
```

). What happens in this case is described in the
documentation for `xyplot`

. Note that in either form,
all the terms in the formula must have the same length after
evaluation.

For the `numeric`

and `factor`

methods, `x`

is the
variable whose histogram or Kernel density estimate is drawn.
Conditioning is not allowed in these cases.

data

For the `formula`

method, an optional data source (usually a
data frame) in which variables are to be evaluated (see
`xyplot`

for details). `data`

should not be
specified for the other methods, and is ignored with a warning if it
is.

type

A character string indicating the type of histogram that is to be
drawn. `"percent"`

and `"count"`

give relative frequency
and frequency histograms respectively, and can be misleading when
breakpoints are not equally spaced. `"density"`

produces a
density histogram.

`type`

defaults to `"density"`

when the breakpoints are
unequally spaced, and when `breaks`

is `NULL`

or a
function, and to `"percent"`

otherwise.

nint

An integer specifying the number of histogram bins, applicable only
when `breaks`

is unspecified or `NULL`

in the call.
Ignored when the variable being plotted is a factor.

endpoints

A numeric vector of length 2 indicating the range of x-values that
is to be covered by the histogram. This applies only when
`breaks`

is unspecified and the variable being plotted is not a
factor. In `do.breaks`

, this specifies the interval that is to
be divided up.

breaks

Usually a numeric vector of length (number of bins + 1) defining the
breakpoints of the bins. Note that when breakpoints are not equally
spaced, the only value of `type`

that makes sense is density.

When `breaks`

is unspecified, the value of
`lattice.getOption("histogram.breaks")`

is first checked. If
this value is `NULL`

, then the default is to use

breaks = seq_len(1 + nlevels(x)) - 0.5

when `x`

is a factor, and

breaks = do.breaks(endpoints, nint)

otherwise. Breakpoints calculated in such a manner are used in all
panels. If the retrieved value is not `NULL`

, or if
`breaks`

is explicitly specified, it affects the display in
each panel independently. Valid values are those accepted as the
`breaks`

argument in `hist`

. In particular, this
allows specification of `breaks`

as an integer giving the
number of bins (similar to `nint`

), as a character string
denoting a method, or as a function.

When specified explicitly, a special value of `breaks`

is
`NULL`

, in which case the number of bins is determined by
`nint`

and then breakpoints are chosen according to the value
of `equal.widths`

.

equal.widths

A logical flag, relevant only when `breaks=NULL`

. If
`TRUE`

, equally spaced bins will be selected, otherwise,
approximately equal area bins will be selected (typically producing
unequally spaced breakpoints).

n

Integer, giving the number of points at which the kernel density is
to be evaluated. Passed on as an argument to `density`

.

panel

A function, called once for each panel, that uses the packet (subset
of panel variables) corresponding to the panel to create a display.
The default panel functions `panel.histogram`

and
`panel.densityplot`

are documented separately, and have
arguments that can be used to customize its output in various ways.
Such arguments can usually be directly supplied to the high-level
function.

allow.multiple, outer

See `xyplot`

.

auto.key

See `xyplot`

.

aspect

See `xyplot`

.

prepanel

See `xyplot`

.

scales

See `xyplot`

.

strip

See `xyplot`

.

groups

See `xyplot`

. Note that the default panel function for
`histogram`

does not support grouped displays, whereas the one
for `densityplot`

does.

xlab, ylab

See `xyplot`

.

xlim, ylim

See `xyplot`

.

drop.unused.levels

See `xyplot`

.

lattice.options

See `xyplot`

.

default.scales

See `xyplot`

.

subscripts

See `xyplot`

.

subset

See `xyplot`

.

default.prepanel

Fallback prepanel function. See `xyplot`

.

weights

numeric vector of weights for the density
calculations, evaluated in the non-standard manner used for
`groups`

and terms in the formula, if any. If this is
specified, it is subsetted using `subscripts`

inside the panel
function to match it to the corresponding `x`

values.

At the time of writing, `weights`

do not work in conjunction
with an extended formula specification (this is not too hard to fix,
so just bug the maintainer if you need this feature).

bw, adjust, width

Arguments controlling bandwidth. Passed on as arguments to
`density`

.

kernel, window

The choice of kernel. Passed on as arguments to
`density`

.

give.Rkern

Logical flag, passed on as argument to `density`

.
This argument is made available only for ease of implementation, and
will produce an error if `TRUE`

.

from, to, cut

Controls range over which density is evaluated. Passed on as
arguments to `density`

.

na.rm

Logical flag specifying whether `NA`

values should be ignored.
Passed on as argument to `density`

, but unlike in
`density`

, the default is `TRUE`

.

…

Further arguments. See corresponding entry in
`xyplot`

for non-trivial details.

An object of class `"trellis"`

. The
`update`

method can be used to
update components of the object and the
`print`

method (usually called by
default) will plot it on an appropriate plotting device.

`histogram`

draws Conditional Histograms, and `densityplot`

draws Conditional Kernel Density Plots. The default panel function
uses the `density`

function to compute the density
estimate, and all arguments accepted by `density`

can be
specified in the call to `densityplot`

to control the output.
See documentation of `density`

for details.

These and all other high level Trellis functions have several
arguments in common. These are extensively documented only in the
help page for `xyplot`

, which should be consulted to learn more
detailed usage.

`do.breaks`

is an utility function that calculates breakpoints
given an interval and the number of pieces to break it into.

Sarkar, Deepayan (2008) *Lattice: Multivariate Data
Visualization with R*, Springer.
http://lmdvr.r-forge.r-project.org/

`xyplot`

,
`panel.histogram`

,
`density`

,
`panel.densityplot`

,
`panel.mathdensity`

,
`Lattice`

# NOT RUN { require(stats) histogram( ~ height | voice.part, data = singer, nint = 17, endpoints = c(59.5, 76.5), layout = c(2,4), aspect = 1, xlab = "Height (inches)") histogram( ~ height | voice.part, data = singer, xlab = "Height (inches)", type = "density", panel = function(x, ...) { panel.histogram(x, ...) panel.mathdensity(dmath = dnorm, col = "black", args = list(mean=mean(x),sd=sd(x))) } ) densityplot( ~ height | voice.part, data = singer, layout = c(2, 4), xlab = "Height (inches)", bw = 5) # }

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