Array index out of range

Pave

I am trying to create my own indicator. I want to calculate an "ADL" line. Here is my code:

    def __init__(self):
        # Add min Period
        self.addminperiod(self.params.period)

        # Aliases to avoid long lines
        c = self.data.close
        h = self.data.high
        l = self.data.low
        v = self.data.volume

        self.data.m = bt.If(bt.Or(bt.And(c == h, c == l), h == l), 0, bt.DivByZero((2 * c - l - h), (h - l), zero=self.p.safezero) * v)
        self.data.adl = self.data.m[-1] + self.data.m

m is calculated correctly. However as ADL requires the current m value and the previous m I ran into a problem:

array index out of range

As m isn't available in the first calculation (I think). So I tried to eliminate the error:

self.data.adl = bt.If(self.data.m[-1] in locals(),self.data.m[-1],0) + self.data.m

Unfortunately this doesn't work. I am very new to backtrader. Maybe some of you can help me.

ab_trader

You can not use [] notation in the init(), only () notation.

Refer to Docs - Platform Concepts - Delayed Indexing.