Usage
panel.histogram(x, breaks, equal.widths = TRUE, type = "density", nint = round(log2(length(x)) + 1),  alpha, col, border, lty, lwd, ..., identifier = "histogram")
Arguments
x
 The data points for which the histogram is to be drawn
breaks
 The breakpoints for the histogram
equal.widths
 logical used when breaks==NULL 
type
 Type of histogram, possible values being "percent",
    "density" and "count"
nint
 Number of bins for the histogram 
alpha, col, border, lty, lwd
    graphical parameters for bars; defaults are obtained from the
    plot.polygon settings.
  
...
 other arguments, passed to hist when
    deemed appropriate  identifier
    A character string that is prepended to the names of grobs
    that are created by this panel function.