SMA — Simple Moving Average

The simple moving average of the last N bars of the input.

Signature

SMA(period, on=<source>)

Argument	Type	Required	Notes
period	int Param or literal	Yes	Number of bars to average. Must be ≥ 2.
on=	symbol, OHLCV field, or indicator	No	Source. Defaults to the trade symbol’s close.

Formula

$$ \text{SMA}t = \frac{1}{N} \sum{i=0}^{N-1} \text{close}_{t-i} $$

Or simply: the average of the last N closes.

Warmup

period bars. SMA is 0 until period closes have been observed.

Reading the value

sma.value             # current value
sma.value_at(1)       # value from the previous bar
sma > 100             # comparison with a number
sma > other_sma       # comparison with another single-value indicator
sma.crossed_above(slow)
sma.crossed_below(slow)

Example

class MACross(Strategy):
    """Golden-cross trend follower."""
    fast = Param(7, min=2, max=50)
    slow = Param(21, min=10, max=200)
    trade = Symbol()
    sizing = FixedCapital()

    def execute(self):
        fast = SMA(self.fast, on=self.trade)
        slow = SMA(self.slow, on=self.trade)

        self.stop_loss(2.0)

        if fast.crossed_above(slow) and self.trade.is_flat:
            self.buy(self.trade)

        if fast.crossed_below(slow) and self.trade.is_long:
            self.sell(self.trade, self.trade.position)

Variants

high_sma = SMA(20, on=self.trade.high)        # SMA of highs
vol_sma = SMA(30, on=self.trade.volume)       # SMA of volume
sma_of_rsi = SMA(5, on=RSI(14, on=self.trade))  # chained — smoothed RSI

Notes

• SMA assigns equal weight to every bar in the window. For more weight on recent bars, use EMA.
• period=1 is technically allowed but produces a 1-bar lag of the source — usually you want to read the source directly.
• For “yesterday’s close” tricks, SMA(1, on=self.trade.close).value_at(1) returns the previous bar’s close.