The TS_SMOOTH function computes central, backward, or forward moving averages of an n-element time-series. Autoregressive forecasting and backcasting are used to extrapolate the time-series and compute a moving average for each point.
This routine is written in the IDL language. Its source code can be found in the file
ts_smooth.pro in the
lib subdirectory of the IDL distribution.
Result = TS_SMOOTH( X, Nvalues [, /BACKWARD] [, /DOUBLE] [, /FORWARD] [, ORDER=value] )
The result is an n-element vector of the same data type as the input vector.
An n-element single- or double-precision floating-point vector containing time-series samples. Note that n must be greater than or equal to 11.
A scalar of type integer or long integer that specifies the number of time-series values used to compute each moving-average. If central-moving averages are computed (the default), this parameter must be an odd integer greater than or equal to three.
Set this keyword to compute backward-moving averages. If BACKWARD is set, the Nvalues argument must be an integer greater than one.
Set this keyword to force the computation to be done in double-precision arithmetic.
Set this keyword to compute forward-moving averages. If FORWARD is set, the Nvalues argument must be an integer greater than one.
An integer or long-integer scalar that specifies the order of the autoregressive model used to compute the forecasts and backcasts of the time-series. By default, a time-series with a length between 11 and 219 elements will use an autoregressive model with an order of 10. A time-series with a length greater than 219 will use an autoregressive model with an order equal to 5% of its length. The ORDER keyword is used to override this default.
; Define an n-element vector of time-series samples: X = [6.63, 6.59, 6.46, 6.49, 6.45, 6.41, 6.38, 6.26, 6.09, 5.99,$ 5.92, 5.93, 5.83, 5.82, 5.95, 5.91, 5.81, 5.64, 5.51, 5.31,$ 5.36, 5.17, 5.07, 4.97, 5.00, 5.01, 4.85, 4.79, 4.73, 4.76] ; Compute the 11-point central-moving-averages of the time-series: PRINT, TS_SMOOTH(X, 11)
6.65761 6.60592 6.54673 6.47646 6.40480 6.33364 6.27000 6.20091 6.14273 6.09364 6.04455 5.99000 5.92273 5.85455 5.78364 5.72636 5.65818 5.58000 5.50182 5.42727 5.34182 5.24545 5.15273 5.07000 5.00182 4.94261 4.87205 4.81116 4.75828 4.71280
SMOOTH, TS_DIFF, TS_FCAST