feat(log): allows zero and negativ values

[callepaeth]

There are problems when using axis of type 'log' with zero and negative values.

This change allow zero and negative values, when useing type 'log' for an axis.

src/coord/axisAlignTicks.ts and src/scale/Log.ts will use log() as mathLog from src/util/math.ts.

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[Ovilia]

Logarithms of zero and negative numbers are not defined in the real numbers. So I don't think it's proper to support this.

[callepaeth]

Logarithms of zero and negative numbers are not defined in the real numbers. So I don't think it's proper to support this.

I understand this. It was the minimal change to support it.
What about going deeper, and change only the functions where the special handling is needed ?

scale/Log.ts:{setExtent,unionExtent,contain,normalize}
coord/axisAlignTicks.ts:alignScaleTicks

If yes, how should it be done ? create a function ? programm it out ?
if using a function, how should it be named ?

regards.

[callepaeth]

After thinking about it ...

What about naming the function in util/math.ts 'symlog' or 'synmetricLog' and use it only where it's needed in:
scale/Log.ts:{setExtent,unionExtent,contain,normalize}
coord/axisAlignTicks.ts:alignScaleTicks

regards.

[Ovilia]

Could you be more specific about in what scenerio do you need this feature?

[callepaeth]

I will prepare an example.

[callepaeth]

balance.txt

Here the example. The chart is more compact with 'log'.
I found some other problems, so the MR is not so good, I will change it.

regars

[callepaeth]

I have done some test. Modifiy 'log' is not the solution, what I really want is 'logvalue'
that behave like 'value' but with a logarithmic scale.
I will prepare that and will make a new MR.

regards.