lattice (version 0.7-4)

histogram: Histograms and Kernel Density Plots

Description

Draw Histograms and Kernel Density Plots

Usage

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,
            ...)

Arguments

formula

A formula of the form ~ x | g1 * g2 * ... indicates that histograms of x should be produced conditioned on the levels of the (optional) variables g1,g2,.... When the conditioning variables g1,g2,...

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 histogra

nint

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

endpoints

vector of length 2 indicating the range of x-values that is to be covered by the histogram. Again, applies only when breaks is unspecified.

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 brea

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 space

n

number of points at which density is to be evaluated

plot.points

logical specifying whether the x values should be plotted.

ref

logical specifying whether a reference x-axis should be drawn.

...

other arguments. 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 calculate

Value

• An object of class ``trellis'', plotted by default by print.trellis.

synopsis

histogram(formula, data = parent.frame(), allow.multiple = FALSE, outer = FALSE, auto.key = FALSE, aspect = "fill", layout = NULL, panel = "panel.histogram", prepanel = NULL, scales = list(), strip = TRUE, groups = NULL, xlab, xlim, ylab, ylim, type = c("percent", "count", "density"), nint = if (is.factor(x)) length(levels(x)) else round(log2(length(x)) + 1), endpoints = extend.limits(range(x[!is.na(x)]), prop = 0.04), breaks = if (is.factor(x)) seq(0.5, length = length(levels(x))+1) else do.breaks(endpoints, nint), equal.widths = TRUE, ..., subscripts = !is.null(groups), subset = TRUE)

densityplot(formula, data = parent.frame(), allow.multiple = FALSE, outer = FALSE, auto.key = FALSE, aspect = "fill", layout = NULL, panel = if (is.null(groups)) "panel.densityplot" else "panel.superpose", prepanel = NULL, scales = list(), strip = TRUE, groups = NULL, xlab, xlim, ylab, ylim, bw = NULL, adjust = NULL, kernel = NULL, window = NULL, width = NULL, give.Rkern = FALSE, n = 50, from = NULL, to = NULL, cut = NULL, na.rm = NULL, ..., panel.groups = "panel.densityplot", subscripts = !is.null(groups), subset = TRUE)

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.

See Also

xyplot, panel.histogram, density, panel.densityplot, panel.mathdensity, Lattice

Examples

data(singer)
histogram( ~ height | voice.part, data = singer, nint = 17,
          endpoints = c(59.5, 76.5), layout = c(2,4), aspect = 1,
          xlab = "Height (inches)")
## The following would not be possible in S-Plus
histogram( ~ height | voice.part, data = singer,
          xlab = "Height (inches)", type = "density",
          panel = function(x, ...) {
              panel.histogram(x, ...)
              panel.mathdensity(dmath = dnorm,
                                args = list(mean=mean(x),sd=sd(x)))
          } )
densityplot( ~ height | voice.part, data = singer, layout = c(2, 4),  
            xlab = "Height (inches)", bw = 5)