HoltsMethod

Holt's method (see: otexts.com/fpp2/holt.html)
Holt (1957) extended simple exponential smoothing to allow the forecasting of data with a trend.
This method involves a forecast equation and two smoothing equations (one for the level and one for the trend):

Forecast equation: ŷ = l + h * b
Level equation: l = alpha * y + (1 - alpha) * (l[1] + b[1])
Trend equation: b = beta * (l - l[1]) + (1 - beta) * b[1]
where h is a step forward or lookahead