histogram {lattice}  R Documentation 
Draw Histograms and Kernel Density Plots, possibly conditioned on other variables.
histogram(formula, data, type = c("percent", "count", "density"), nint = if(is.factor(x)) length(levels(x)) else round(log2(length(x))+1), endpoints = range(x[!na.x]), breaks = if(is.factor(x)) seq(0.5, length = length(levels(x)) + 1) else do.breaks(endpoints, nint), equal.widths = FALSE, ...) densityplot(formula, data, n = 50, plot.points = TRUE, ref = FALSE, ...) do.breaks(endpoints, nint)
formula 
A formula of the form ~ x  g1 * g2 * ...
indicates that histograms or Kernel Density estimates of x
should be produced conditioned on the levels of the (optional)
variables g1,g2,... . When the conditioning variables
g1,g2,... are missing, the leading ~ can be dropped.
x can be numeric (or factor for histogram ), and each
of g1,g2,... must be either factors or shingles.
As a special case, the right hand side of the formula ( x ) can
actually contain more than one variable separated by a '+'
sign. What happens in this case is described in details in the
documentation for xyplot .

data 
optional data frame in which variables are to be evaluated 
type 
Character string indicating type of histogram to be
drawn. ``percent'' and ``count'' give relative frequency and
frequency histograms, and can be misleading when breakpoints are not
equally spaced. ``density'' produces a density scale histogram.
type defaults to ``percent'', except when the breakpoints
are unequally spaced or breaks = NULL , when it defaults to
``density''.

nint 
Number of bins. Applies only when breaks is unspecified in
the call.

endpoints 
vector of length 2 indicating the range of xvalues that is to be
covered by the histogram. Again, applies only when breaks is
unspecified. In do.breaks , this specifies the interval that
is to be divided up.

breaks 
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.
Usually all panels use the same breakpoints. This can be changed by specifying breaks = NULL . This has the effect of letting each
panel choose its own breakpoints. The choice of these breakpoints
are made as follows: The number of bins is calculated by the formula
for nint above, and then breakpoints are chosen according to
the value of equal.widths .

equal.widths 
logical, relevant only when breaks=NULL .
If TRUE , equally spaced bins will be selected, otherwise,
approximately equal area bins will be selected (this would mean that
the breakpoints will not be equally spaced).

n 
number of points at which density is to be evaluated 
plot.points 
logical specifying whether the x values
should be plotted along the y=0 line.

ref 
logical specifying whether a reference xaxis should be drawn. 
... 
other arguments, passed along to the panel function. In
the case of densityplot , if the default panel function is
used, then arguments appropriate to density can be
included. This can control the details of how the Kernel Density
Estimates are calculated. See documentation for
density for details.

histogram
draws Conditional Histograms, while
densityplot
draws Conditional Kernel Density Plots. The
density estimate in densityplot
is actually calculated using
the function density
, and all arguments accepted by it can be
passed (as ...
) in the call to densityplot
to control
the output. See documentation of density
for details. (Note:
The default value of the argument n
of density
is
changed to 50.)
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.
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.
The form of the arguments accepted by the default panel function
panel.histogram
is different from that in SPLUS. Whereas
SPLUS calculates the heights inside histogram
and passes only
the breakpoints and the heights to the panel function, here the
original variable x
is passed along with the breakpoints. This
allows plots as in the second example below.
Deepayan Sarkar Deepayan.Sarkar@Rproject.org
xyplot
,
panel.histogram
,
density
,
panel.densityplot
,
panel.mathdensity
,
Lattice
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)