Got IndexError: array index out of range if preload=False

Yacc Don

Hi,

I want to caculate growth each day, so I did like this in strategy:

class UserStockStrategy(bt.Strategy):
    def __init__(self):
        exp_variables["growth"] = (self.data.close - self.data.close[-1])/self.data.close[-1]

Everthing is OK, until I run cerebo with preload=False

    cerebro = bt.Cerebro(runonce=False, preload=False)

The I got IndexError:
IndexError: array index out of range

    exp_variables["growth"] = (self.data.close - self.data.close[-1])/self.data.close[-1]
  File "/home/user/.local/lib/python3.7/site-packages/backtrader/linebuffer.py", line 163, in __getitem__
    return self.array[self.idx + ago]
IndexError: array index out of range

Could anybody help me, thanks

@ab_trader @backtrader

vladisld

@yacc-don please take a look at delayed indexing docs: https://www.backtrader.com/docu/concepts/#lines-delayed-indexing

Yacc Don

@vladisld Thanks