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, the EQUAL method is always used.
  • For even-periodicity series, the keyword EQUAL or CENTERED 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.