Custom Observer for debug arrows on graph, to be called in stratergy, error

HarryBurge

Been trying to make a way I can debug my algorithm visually by using a arrow like BuySell Observer. I want to be able to call addpoint which will add it to the graph, however I have ran into a few problems these include:
Getting an error when trying to call the line outside of the next()

   self.lines.peak[index] = copy.deepcopy(yvalue)
  File "/usr/local/lib/python3.7/site-packages/backtrader/lineseries.py", line 62, in __get__
    return obj.lines[self.line]
AttributeError: 'NoneType' object has no attribute 'lines'

with example code:

def addpoint(self, index, typepoint, yvalue):
        self.lines.peak[index] = copy.deepcopy(yvalue)

Due to this I have been trying to do things through the next function with example code below:

import math
import copy

from backtrader.observer import Observer


class PeaksAndTroofs(Observer):
    lines = ('peak', 'troof',)

    plotinfo = dict(plot=True, subplot=False, plotlinelabels=True)
    plotlines = dict(
        peak=dict(marker='v', markersize=8.0, color='purple',
                 fillstyle='full', ls=''),
        troof=dict(marker='^', markersize=8.0, color='blue',
                  fillstyle='full', ls='')
    )

    params = (
        ('barplot', False),  # plot above/below max/min for clarity in bar plot
        ('bardist', 0.015),  # distance to max/min in absolute perc
    )

    typepoint = []
    yvaluepoint = []
    index = []

    def next(self):

        if self.yvaluepoint != [] and self.typepoint != [] and self.index != []:

            for i in range(len(self.index)):

                if self.typepoint[i] == 'peak':
                    self.lines.peak[self.index[i]] = copy.deepcopy(self.yvaluepoint[i])

                elif self.typepoint == 'troof':
                    self.lines.troof[self.index[i]] = copy.deepcopy(self.yvaluepoint[i])

            self.typepoint = []
            self.yvaluepoint = []
            self.index = []
 

    def addpoint(self, index, typepoint, yvalue):
        self.typepoint.append(copy.deepcopy(typepoint))
        self.yvaluepoint.append(copy.deepcopy(yvalue))
        self.index.append(copy.deepcopy(index))

I don't get any results out onto the graph, I beileve its due to the.

self.typepoint = []
self.yvaluepoint = []
self.index = []

This is due to when removing I get the a sort of expected behavouir with plotting however, indicators are repeated and troofs don't exsist.
This is the graph with the above code commented out.

I am creating my calls to addpoint like this in my stratergy.

if len(self.dataclose) % 10 == 0:
     self.peaks_and_troofs_ob.addpoint(self.peaks_and_troofs_ob, 0, 'peak', self.dataclose[0])
elif len(self.dataclose) % 5 == 0:
            self.peaks_and_troofs_ob.addpoint(self.peaks_and_troofs_ob, 0, 'troof', self.dataclose[0])

And the way I have pulled in the new observer to the stratergy is this in the init

# Plots peaks and troofs
self.peaks_and_troofs_ob = PeaksAndTroofs
self.env.addobservermulti(self.peaks_and_troofs_ob)

vladisld

@HarryBurge said in Custom Observer for debug arrows on graph, to be called in strategy, error:

I am creating my calls to addpoint like this in my strategy.

Few points:

Having a strategy dependent on specific observer is probably not the best idea design-wise.
Why the same logic can't be run right inside the observer? All datas are available for observers AFAIR.