Seasonal Subseries Plot
DESCRIPTION:
Plots the seasonal component of a seasonally decomposed time series.
USAGE: 
monthplot(x, type="l", labels=<<see below>>, xlab="",
        ylab=deparse(substitute(x)))
REQUIRED ARGUMENTS:
x:
a univariate time series, typically the seasonal component of a seasonal adjustment procedure such as sabl or stl. Missing values are not accepted.
OPTIONAL ARGUMENTS:
type:
type of plot to make for each subseries. "l" (the default) means connected lines, "h" means vertical lines (high density plot) and "p" means points.
labels:
vector of labels for each subseries. The default values are: month names if frequency(y) is 12; quarter number, if frequency(y) is 4; digits from 1 to frequency(y), for all other cases.
xlab:
label for the x-axis.
ylab:
y-axis label. This defaults to the expression given for x.

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 plot of seasonal components is produced on the current graphics device.
DETAILS:
The series y is broken into frequency(y) subseries, e.g., the January subseries, the February subseries, etc The plot shows variation about the midmean (25% trimmed mean) of each subseries.
REFERENCES:
Cleveland, W. S. and Terpenning, I. J. (1982). Graphical Methods for Seasonal Adjustment. Journal of the American Statistical Association 77, 52-62.
SEE ALSO:
stl , sabl , sablplot , par .
EXAMPLES: 
fit <- sabl(hstart)
monthplot(window(fit$seasonal, end=end(hstart)))


monthplot(fit$seasonal, type="h",
      main="Seasonal Component of Housing Starts")