[Lens] Line chart styling controls

[ghudgins]

Describe the feature:
Control dot size, show/hide dots, line width, line stroke

Describe a specific use case for the feature:
When My data has missing results in time interval buckets
I need to override the default styling with specific dot size, stroke, and line width
So I can achieve the continuous look and feel even when my data is missing buckets

Related discuss post

Would be good for @gvnmagni to remark as to what we should expose from a vis best practices here (at his leisure or when this is planned for a minor release)

[elasticmachine]

Pinging @elastic/kibana-vis-editors @elastic/kibana-vis-editors-external (Team:VisEditors)

[gvnmagni]

Premise: What I can say is that typically in data visualization missing data values in time series are treated visually different and since it shouldn't happen frequently the tendency is to make the missing data as prominent as possible. For example, by removing completely the lines that should go among them in order to be extremely clear for the user that we have no values and to avoid implicating increase/decrease in values that are a result of a pure graphical interpolation of points with a line.

But this is just a usual case, which I believe does not apply well to us. Since we could have a lot of time buckets without values, I'm seeing a lot of timeseries that are almost unreadable since we have single dots, far from each other, not connected since we have missing values in between.

What I would suggest is to set by default a visual treatment that would draw the lines (maybe instead of interpolating points that are really far from each other, to make the line go to zero and up again when it reaches the bucket with values) and allow the users to customize it according to their needs. But the starting point would be to draw lines in a way that is clear what's happening without compromising the reading of the chart.

On last thing, for the record, I wouldn't allow full customization for the users, I would let them choose among a series of treatments made by us, as it currently is if I'm correct.

[ghudgins]

just an idea (in passing) on how to migrate to new behaviors is to introduce "auto" and turn the existing defaults into a specific configuration.

other problems we are solving if we had better defaults:

• hard to distinguish between multiple lines even with different color

* line does not respond well to changing display size. as the display gets small the line becomes too large.

[flash1293]

+1 https://discuss.elastic.co/t/how-can-i-display-dot-and-value-on-lens-chart/306305

[dej611]

+1 https://discuss.elastic.co/t/reference-line-can-it-vary-over-time/321226/2