MA Subcommand (SEASON command)
MA
specifies
how to treat an even-periodicity series when computing moving averages.
-
MA
should be specified only when the periodicity is even. When periodicity is odd, theEQUAL
method is always used. - For even-periodicity series, the keyword
EQUAL
orCENTERED
can be specified.CENTERED
is the default. -
EQUAL
calculates moving averages with a span (number of terms) equal to the periodicity and all points weighted equally. -
CENTERED
calculates moving averages with a span (number of terms) equal to the periodicity plus 1 and endpoints weighted by 0.5. - The periodicity is specified on the
PERIOD
subcommand.
Example
SEASON VARIABLES = VARY
/MA=CENTERED
/PERIOD=12.
- In this example, moving averages are computed with spans of 13 terms and endpoints weighted by 0.5.