Draw a Dot Chart
DESCRIPTION:
Plots a dot chart from a vector. A grouping variable, and group summary may be used along with other options.

This function is generic (see Methods); method functions can be written to handle specific classes of data. Classes which already have methods for this function include:

crystal.list, crystal.vector, decompose.

USAGE: 
dotchart(data, labels=<<see below>>, groups=NULL, gdata=NULL, horiz=T,
          pch="o", lty=2)
REQUIRED ARGUMENTS:
data:
vector of all data values.
Missing values (NA) are allowed.
OPTIONAL ARGUMENTS:
labels:
vector of labels for the data values. If this is missing, labels are taken from the names of data.
groups:
categorical variable used for splitting the data vector into groups and providing group labels.
gdata:
vector of group data, that is, an overall value for each group. This could be a sum or an average, for example.
horiz:
logical flag: should data values be on horizontal or vertical axis?
pch:
character to be used as the plot character.
lty:
line type used in drawing the dotted line.

Graphical parameters may also be supplied as arguments to this function (see par). In addition, the high-level graphics arguments described under par and the arguments to title may be supplied to this function.

SIDE EFFECTS:
a chart is plotted with all elements of groups together, and the elements identified with labels, if present.
DETAILS:
Missing values and Infs are not plotted.
SEE ALSO:
barplot , boxplot , par , title .
EXAMPLES: 
# a simple function to make dotcharts from matrices with dimnames
dotchart.mat <- function(mat, col.is.main = T, ...)
{
        if(col.is.main)
                mat <- t(mat)
        g.lab <- dimnames(mat)[[2]]
        if(length(g.lab))
                g <- factor(col(mat), labels = g.lab)
        else g <- factor(col(mat))
        la.lab <- dimnames(mat)[[1]]
        if(length(la.lab))
                la <- factor(row(mat), labels = la.lab)
        else la <- factor(row(mat))




        dotchart(mat, labels = la, groups = g, ...)
        invisible()
}




perc.data <- c(5.4, 3.1, 3.5, 5.7, 8.6, 25.0, 20.4,
        26.0, 22.0, 36.3, 34.1, 28.0, 14.4, 11.4, 4.5)
percent <- matrix(perc.data,ncol=3, byrow=T)
community <- c("Old Suburb", "Coast County", "New Suburb")
service <- c("Child Care", "Health Services",
      "Community Centers", "Family & Youth", "Other")
com <- factor(col(percent), label=community)
serv <- factor(row(percent), label=service)


dotchart(percent, labels=com, group=serv)


dotchart(percent, labels=serv, group=com, horiz=F)


# now plot the same thing with the median percent for each service


gmed <- tapply(percent, com, median)
dotchart(percent, labels=serv, group=com, gdata=gmed)