Custom indicator - lines connecting candles dont show up (eg zigzag indicator lines) about btplotting

[Jake0303]

@viveksp were you able to fix it at all? PSAR indicator isn't working at all

[happydasch]

Go ahead with the PR. I replaced lately some markers which did not work, too

[loopiezlol]

@Jake0303 I encountered the same issue with PSAR in backtrader-plotting, which this lib is based on

found out it's related to the marker type used. this commit did the trick for me loopiezlol/backtrader_plotting@67753b9

I assume "point" or "pixel" would've worked as well, but "dot" doesn't seem to be a valid choice https://matplotlib.org/stable/api/markers_api.html

[loopiezlol]

@happydasch I'm happy to create a PR trying to fix any invalid matplotlib markers for this repo, but I am curious to learn whether this repo is still maintained beforehand

[happydasch]

7ca6297

[tlchan5]

@happydasch and @loopiezlol Thanks for proposing the solution.
Just happened that I uses the same indicator and hitted the same issue.
I gave a try to the solution but the issue still exists. Same as @viveksp, the line plotting looks okay when plotting with the original backtrader plot.

I think the problem is btplotting unable to plot the line / connect the point if the value = NaN
The indicator marks the peak / valley with a value and others are set to NaN. The original backtrader plot is able to connect the point at peak & valley and ignore the NaN in between (just like
https://user-images.githubusercontent.com/3601042/108806710-731b2580-75c8-11eb-889b-07f1c0bdbf08.PNG))

I checked the implemenation of the indicator plotting in backtrader. There's a lineplotinfo._get(_skipnan, False) check in plot.py (https://github.com/mementum/backtrader/blob/master/backtrader/plot/plot.py#L466)
I wonder does the btplotting apply the same check and consider the "_skipnan" attributes when plotting the line?

I am not familiar with the rendering / plotting code so I cannot help much in this case. Hopefully this can point to the correct solution.

[happydasch]

latest code should be able to plot this, reopen if still not plotting corrrectly