Stacked stepped time lines does not rendering correctly

[davideferre]

I've a stacked stepped time lines chart that seems to render uncorrect values randomly.
This is the screenshot of the problem:

This is the codpen link to the bug reproduction: https://codepen.io/davideferre/pen/XWNxLKp

I'm using 2.9.4 chart.js version.

As you can see in the screenshot or in codepen the first two point of the violet COMP12 line are 1 and 0 but they are at the same height on the Y axis.
Sometimes the line render correctly but when I try to disable a dataset the other datasets fall on the same behavior.
Am I doing something wrong or this is a bug?

[kurkle]

In 2.9 the stacking is based on the array index of the values. So you'd need to make sure each data array contains value (or undefined/NaN) for each point. Or you could upgrade to v3 beta.

[davideferre]

In 2.9 the stacking is based on the array index of the values. So you'd need to make sure each data array contains value (or undefined/NaN) for each point. Or you could upgrade to v3 beta.

I've created another codepen trying your suggestions but it doesn't working anymore with 2.9v:

https://codepen.io/davideferre/pen/yLVQNGB

The purple line takes 3 values ​​0,1 and 2 while I would have expected it to take only 2

[etimberg]

It appears better when the data goes in as just an array of values. https://codepen.io/etimberg/pen/oNYQjQa

[davideferre]

It appears better when the data goes in as just an array of values. https://codepen.io/etimberg/pen/oNYQjQa

I can't draw chart as you suggest because the lines appear overlapping.
I've created another codepen with the null values where they don't have a specific value, but as you can see on the purple line (COMP12) the second point is 1 and the third is 0 but they are at the same level.
Moreover in the point where there is the peak of the purple line the previous point is already 1 but it is at the same level as the zero points.
https://codepen.io/davideferre/pen/gOLJwao

[kurkle]

Are you trying to have "comp22" in range 0..1 , "comp12" in range 1..2 etc. independent on the other values?

"stacked" means the values are added. at index 0 you have 0 and 1 = 1, index 1 you have 1 and 0 = 1

You should set the hover and tooltip modes to index to highlight and see the values that are stacked together.

https://codepen.io/kurkle/pen/MWbdbVo