Ema Slope indicator

[ThinkWaitFast]

Hello, I'm new to backtrader and currently trying to build a really simple custom indicator (EMA slope). I'm having trouble accessing past values of the ema, can anyone point me in the right direction?

[rho33]

Is this along the lines of what you're trying to do?

class EMASlope(bt.Indicator):
    lines = ('slope',)
    
    def __init__(self):
        self.ema = bt.indicators.ExponentialMovingAverage()
    
    def next(self):
        self.l.slope[0] = self.ema[0] - self.ema[-1]

If it really is this simple you could also just calculate it inside your strategy's next method

class MyStrat(bt.Strategy):
    
    def __init__(self):
        self.ema = bt.indicators.ExponentialMovingAverage()

    def next(self):
        slope = self.ema[0] - self.ema[-1]

I'm relatively new to backtrader too and I looked at this page to get this awnser https://www.backtrader.com/docu/inddev/

[run-out]

For a vectorized approach you can use:

class EMASlope(bt.Indicator):
    lines = ('slope',)
    
    def __init__(self):
        self.ema = bt.indicators.ExponentialMovingAverage()
        self.ema2 = self.ema - self.ema(-1)

[rho33]

@run-out said in Ema Slope indicator:

self.ema2 = self.ema - self.ema(-1)

Yeah this approach is probably better because it automatically updates the indicator's minimum period.