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📈 Holt-Winters Seasonal Forecasting
Triple exponential smoothing: level + trend + seasonality, forecast ahead (seasonal period = 1 reduces to double exponential with trend)
Parameters
Notes
· Holt-Winters (additive): l_t=α(y_t−s_{t−m})+(1−α)(l_{t−1}+b_{t−1}); b_t=β(l_t−l_{t−1})+(1−β)b_{t−1}; s_t=γ(y_t−l_t)+(1−γ)s_{t−m}; forecast F_{t+k}=l_t+k·b_t+s_{t−m+((k−1) mod m)}. When m=1 it reduces to Holt with trend (double exponential).
· A series length of at least 2×m is recommended to initialize the seasonal component.
About Holt-Winters Forecasting Calculator
Forecast seasonal series with Holt-Winters triple exponential smoothing: auto-optimized α, β, γ and additive or multiplicative seasonal models.
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