SEASONAL SUBSERIES PLOT

SEASONAL SUBSERIES PLOT

Graphics Command

Generates a seasonal subseries plot.

A seasonal subseries plot is used to determine if there is significant seasonality in a time series. Instead of a straight time order plot, it splits the plot into the corresponding seasons (or periods). For example, for monthly data, all the January values are plotted, then all the February values, and so on. Reference lines are drawn at the seasonal means.

LET PERIOD = <value>
LET START = <value>


SEASONAL SUBSERIES PLOT <y>
                        <SUBSET/EXCEPT/FOR qualification>
where <y> is the response variable;
and where the <SUBSET/EXCEPT/FOR qualification> is optional.

The LET command is uses to define the period (e.g., the period for monthly data is typically 12) and the start value. The start value is used when the data do not start in the first unit of the period (e.g., if you have monthly data that starts in March instead of January, you would use LET START = 3).

LET PERIOD = 12
LET START = 3
SEASONAL SUBSERIES PLOT Y


LET PERIOD = 4
LET START = 1
SEASONAL SUBSERIES PLOT Y

The sample program below shows how to use various plot control commands to label the plot.

None

None

RUN SEQUENCE PLOT	= Generates a run sequence plot.
SPECTRAL PLOT	= Generate a spectral plot.
AUTOCORRELATION PLOT	= Generate an autocorrelation plot.
ARMA	= Fit an ARMA model.
SEASONAL LOWESS	= Generate a lowess based trend/seasonality/residual decomposition of a time series.

Cleveland, William S. (1993), "Visualizing Data", Hobart Press,

Time Series Analysis

2000/1

skip 25
read mlco2mon.dat co2 date year month
.
. Linear Fit to Detrend Data
.
fit co2 date
let co2res = res
.
. Seasonal Subseries Plot
.
xlimits 7 167
xtic offset 7 7
major xtic mark number 12
minor xtic mark number 0
x1tic mark label format alpha
x1tic mark label content Jan Feb Mar Apr May June July Aug Sep ...
Oct Nov Dec
x1label Month
y1label CO2 Concentrations
let period = 12
let start = 5
title Seasonal Subseries Plot of CO2 Concentrations
seasonal subseries plot co2res