Horizontally Shifted Bar Plots
Description
This function is a modified version of barplot
with an
additional argument that allows the bars to be shifted left or right
along the xaxis.
Usage
1 2 3 4 5 6 7 8 9 10  barplot2(height, width = 1, space = NULL,
names.arg = NULL, legend.text = NULL, beside = FALSE,
horiz = FALSE, density = NULL, angle = 45,
col = NULL, border = par("fg"),
main = NULL, sub = NULL, xlab = NULL, ylab = NULL,
xlim = NULL, ylim = NULL, xpd = TRUE, log = "",
axes = TRUE, axisnames = TRUE,
cex.axis = par("cex.axis"), cex.names = par("cex.axis"),
inside = TRUE, plot = TRUE, axis.lty = 0, offset = 0,
add = FALSE, args.legend = NULL, x.offset = 0, ...)

Arguments
height 
either a vector or matrix of values describing the
bars which make up the plot. If 
width 
optional vector of bar widths. Recycled to length the
number of bars drawn. Specifying a single value will have no
visible effect unless 
space 
the amount of space (as a fraction of the average bar
width) left before each bar. May be given as a single number or
one number per bar. If 
names.arg 
a vector of names to be plotted below each bar or
group of bars. If this argument is omitted, then the names are
taken from the 
legend.text 
a vector of text used to construct a legend for
the plot, or a logical indicating whether a legend should be
included. This is only useful when 
beside 
a logical value. If 
horiz 
a logical value. If 
density 
a vector giving the density of shading lines, in
lines per inch, for the bars or bar components.
The default value of 
angle 
the slope of shading lines, given as an angle in degrees (counterclockwise), for the bars or bar components. 
col 
a vector of colors for the bars or bar components.
By default, grey is used if 
border 
the color to be used for the border of the bars.
Use 
main,sub 
overall and sub title for the plot. 
xlab 
a label for the x axis. 
ylab 
a label for the y axis. 
xlim 
limits for the x axis. 
ylim 
limits for the y axis. 
xpd 
logical. Should bars be allowed to go outside region? 
log 
string specifying if axis scales should be logarithmic; see

axes 
logical. If 
axisnames 
logical. If 
cex.axis 
expansion factor for numeric axis labels. 
cex.names 
expansion factor for axis names (bar labels). 
inside 
logical. If 
plot 
logical. If 
axis.lty 
the graphics parameter 
offset 
a vector indicating how much the bars should be shifted relative to the x axis. 
add 
logical specifying if bars should be added to an already
existing plot; defaults to 
args.legend 
list of additional arguments to pass to

x.offset 
shifts the plot left or right along the xaxis. 
... 
arguments to be passed to/from other methods. For the
default method these can include further arguments (such as

Details
barplot2
is a slightly modified version of
barplot.default
with an additional parameter (x.offset
)
that can shift the plot left or right. It was originally written for
use by barplot.tis
, but it can now also be called on it's own.
Value
same as barplot.default
, i.e.,
A numeric vector (or matrix, when beside = TRUE
), say
mp
, giving the coordinates of all the bar midpoints
drawn, useful for adding to the graph.
If beside
is true, use colMeans(mp)
for the
midpoints of each group of bars, see example.
See Also
barplot
, barplot.tis