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* Example TABLE6-7.DAT from page 218
*
open data table6-7.dat
data(format=free,org=columns) 1 30 data
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filter(type=lagging,width=3) data / ma3
filter(type=lagging,width=3) ma3 / ma3x3
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set a = 2*ma3-ma3x3
set b = 2.0/(3-1)*(ma3-ma3x3)
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set forecast = a{1}+b{1}
set error    = data-forecast
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print(picture="*.##") / data ma3 ma3x3 a b forecast error
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graph(footer="Figure 6-4. Single and Double Moving Averages",key=below) 4
# data
# ma3
# ma3x3
# forecast