Indicator development - missing a key piece

cemdev

I'm still not sure when to use init and when to use next.

The indicator I'm trying to build is simple.

it's effectively: (i'm making up the actual formula, as this one is proprietary, but it's all regular variables off the data object)

if the close > last close then x, if close < last close then y, if close == lastclose then 0

effectively, what i want is:

x = self.data.close - self.data.close(-1) * self.data.high
y = self.data.close(-1) - self.data.close * self.data.high

self.lines.myindicator = x if close > close(-1) else y if close < close(-1) else 0

but that throws an error, and i'm really not sure where to start, there's so much about the indicators I don't really get at this point.

bool should return bool, returned LineOwnOperation

effectively - can I run boolean operations in init? if so, how? if not - then I guess I have to do this in next - but I run into trouble there too.

cemdev

never mind, solved by using next

backtrader

@cemdev said in Indicator development - missing a key piece:

x =  self.data.close - self.data.close(-1) * self.data.high
y =  self.data.close(-1) - self.data.close * self.data.high
self.lines.myindicator =  x if close > close(-1) else y if close < close(-1) else 0

(Use ``` to quote code blocks)

The above is almost ok for __init__. The problem being that not everything in python can be overridden and if ... elif ... else is one of those things. One needs to use backtrader.If (capital I to distinguish it even with from backtrader import *)

See here: Docs - Platform Concepts, specifically the section Some non-overriden operators/functions

With that in mind

self.lines.myindicator =  bt.If(close > close(-1), x, bt.If(close < close(-1), y, 0))

Which effectively says: if close > close(-1) then x elif close < close(-1) then y else 0

cemdev

oh, that is EXCELLENT. Many thanks for the responses, especially on a sunday. i have it working with next, but i'll refactor with this, seems much cleaner.