One for the cookbook: On Balance Volume

[Rudi]

@backtrader Not developed by myself but a valuable indicator. Credits go to backtest rookies

class OnBalanceVolume(bt.Indicator):
    alias = 'OBV'
    lines = ('obv')
    params = (
      ('length', 12),
    )

    plotlines = dict(
        obv=dict(
            _name='OBV',
            color='purple',
            alpha=0.50
        )
    )

    def __init__(self):

        # Plot a horizontal Line
        self.plotinfo.plotyhlines = [0]

    def next(self):

        # Aliases to avoid long lines
        c = self.data.close
        v = self.data.volume
        obv = self.lines.obv

        if c[0] > c[-1]:
            obv[0] = obv[-1] + v[0]
        elif c[0] < c[-1]:
            obv[0] = obv[-1] - v[0]
        else:
            obv[0] = obv[-1]