inconsistency in the scaling of the y-axes

[michkami]

Description

In the example below we have 3 data rows.
Data1 and Data2 are grouped and assigned to the y-Axis.
Data3 is assigned to the y2-Axis.
When setting bar.zerobased: false it results in following chart:

I would expect the y2-Axis to be also scaled like the y-Axis, as all values on this axis are positive too.
I see no reason here to treat the y2-axis differently from the y-axis in this case.

The same happens when the data is not grouped at all:

In this case data3 on y2-axis is not scaled.

Using bar.zerobased: true leads to following and correct result:

Removing data2 from the chart and setting bar.zerobased: false results in this chart:

Here I would also expect for both axes to be scaled like the Y-Axis in Screenshot 1 (the stacked bars)

bar.zerobased: true scales as expected:

Having 2 grouped data rows on each axis results in both being scaled correctly:

Same with all 4 data rows being not grouped:

Overall, it seems like there is an inconsistency how the grouped data affects the scaling of the y-axes. It seems like you need at least 2 data rows per group for the scaling to work as expected.

Is the "wrong" behavior I described above the expected behavior, or can we classify this as a bug?

Steps to check or reproduce

https://jsfiddle.net/michkami/a9uzyrs8/

[netil]

@michkami
When there're 2 or more values aligned to single axis(y or y2), the domain range will set according it.

Let's say, given values are 300 and 500, in this case, min=300 and max=500.
But when single value (ex. 500) is given, can't determine min/max, because there's no data to determine or compare.

So, in this case min will be set as 0 and max 500.
https://github.com/naver/billboard.js/blob/master/src/ChartInternal/internals/domain.ts#L136

[michkami]

@michkami When there're 2 or more values aligned to single axis(y or y2), the domain range will set according it.

Let's say, given values are 300 and 500, in this case, min=300 and max=500. But when single value (ex. 500) is given, can't determine min/max, because there's no data to determine or compare.

So, in this case min will be set as 0 and max 500. https://github.com/naver/billboard.js/blob/master/src/ChartInternal/internals/domain.ts#L136

I see, this makes sense.

Maybe not completely connected to the question above, but I found this line here

billboard.js/src/ChartInternal/internals/domain.ts

Line 143 in 487a129

// Cancel zerobased if axis_*_min / axis_*_max specified

which cancels the zerobased setting when y min or max is set. But in case of y.min: 0 or y.max: 0 I would still expect the zerobased option put the zero on the x axis level.

Do you see any reason to not add an exception for the 0 values here?

In this case I would expect the zerobased option to still be working:
https://jsfiddle.net/michkami/6vr1z20f/

[netil]

Do you see any reason to not add an exception for the 0 values here?

The conditional stayed from the start of the project and maintained as, mainly to not break any possible issue.
https://github.com/naver/billboard.js/blob/1.0.0/src/internals/domain.js#L156

[michkami]

The conditional stayed from the start of the project and maintained as, mainly to not break any possible issue. https://github.com/naver/billboard.js/blob/1.0.0/src/internals/domain.js#L156

Yes, I saw this. My question was if there it would be possible to add 0 as an exception here in case zerobased is true, so that the y axis will start on the x axis level when min is set to 0.

The current behaviour is what i would only expect if I set zerobased: false and then set the min value to 0.
If zerobased: true and I set the y axis min to 0, I would expect for it to start at the same level as the x axis.
I played around and saw, that if i pass null to y axis min, it would in this case work as expected, but the types only accept number | undefined.