SMOOTHIE evaluates time-series data to construct a forecasting model using single and double exponential smoothing, moving average, trend, arithmetic mean, and complete decomposition methods.

Input requirements.

• Title. The user should enter a title for the data in the top form field.
• Observations. A set of time-series data in free format: a series of observed values for a single variable, taken at uniform time intervals, given in chronological order, and separated by blanks or on separate lines.
• Number of periods for error calculations. the number of observations to be used in calculating cumulative error values, such as mean squared error (MSE). Since the models result in varying numbers of historical error terms, one may wish to use a subset in computing cumulatives, if the values are to be compared across models.
• Choice of forecasting model. Using the radio buttons, one of the following forecasting models is selected and any related parameter values entered:
• Moving average, requires: number of periods to average over
• Exponential smoothing (single), requires: alpha, a smoothing constant between 0 and 1
• Smoothing with trend (double), requires: alpha (0-1, emphasis on recent values) and beta (0-1, weight on trend component)
• Trend, fits regression line to data using time as the independent variable
• Arithmetic mean, forecast is the average of all historical values
• Decomposition of data into trend, seasonal, cyclical, and irregular/random components, requires: specification of monthly or quarterly nature of data

Sample data

The following quarterly data may be copied and pasted into the Input time-series data here field.

13.1 12 15.8 11.4 14 15.3 17.6 13 15.2 16.4
19.2 14.7 15.6 15.5 17.2 16.7 16.8 16.5 17.4
14.4 17.0 19.4 19.2 16.7

Add a title, select a forecasting model, and press the Run Smoothie button.

Sample dataset 2

Quarterly new car sales in U.S., 1958-1974

1069  1142  927   1151
1323  1613  1289  1263
1515  1739  1330  1559
1212  1550  1180  1624
1559  1887  1360  1946
1721  2056  1498  2059
1844  2171  1753  1895
2196  2381  1822  2366
2207  2209  1744  2218
1744  2235  1692  1897
2021  2321  1934  2349
2030  2347  1927  2161
1782  2189  1654  1490
1977  2281  1988  2676
2078  2537  2165  2541
2473  2742  2247  2208
1771  2166  1949  1562

In-class example:

120 124 122 123 125 128 129 127 129 128 130

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