Signal (fynance.signal)

The bridge from predictions to positions: mappers and a model+mapper pipeline.

The anti-churn mappers (ema_smooth, deadband, min_hold) are stateful but strictly causal; compose them on top of a position to cut turnover where transaction costs would otherwise dominate (high fees / high frequency). They pair with the train-time turnover penalty in ObjectiveModel (its cost argument).

sign(pred)	Long/short by the sign of the prediction (+1 / -1 / 0).
threshold(pred[, long, short])	Position with a flat dead-band.
rank(pred, top, bottom)	Cross-sectional long/short by rank.
vol_target_position(signal, prices[, ...])	Scale a directional signal by causal volatility-targeting leverage.
ema_smooth(pred[, alpha])	Causally smooth a position with an exponential moving average.
deadband(pred[, band])	Hold the previous position unless the target moves by more than band.
min_hold(pos, hold[, tol])	Enforce a minimum holding period between position changes.
SignalPipeline(model, mapper[, mapper_kwargs])	A SignalModel plus a position mapper.