feat: allow LinePlot to be drawn in steps

[larshei]

Changes

Many timeseries depict a "state" of some sort that was measured at specific points in time.

Simply drawing a line between the points of measurement often feels weird to me. I rather think "the value has been y from t1 to t2, then at t2 we got a new value".

So I added a style for line graphs that creates a LinePlot with steps:

As we no longer have two options (smooth yes/no) but three options,
the interface needed to be changed:

The option is now called plot_type, with the options

• :direct
• :smooth
• :step

If plot_type is not provided, we fall back to the smoothed option.

[mindok]

Thanks @larshei - it looks great!

It is a breaking change to the API so what I might do is add back the :smoothed keyword option and map it into your new :plot_style option behind the scenes and note the :smoothed option as deprecated in the documentation.

Edit: Just saw the last commit 🙄

[mindok]

Should this be:

plot_style = if smoothed != nil, do: :smooth, else: style

(i.e. :smoothed atom set)

[mindok]

Ah - I see what you've done - the true/false is handled in the path logic. I think it's better to definitively set the plot_style here for a couple of reasons:

1. We isolate the deprecation logic to a single spot
2. The paths code may be used from elsewhere in the future and the options (true, false, :smooth, :direct, :step) are overlapping and unclear
3. There are fewer places to go to remove the deprecated code

so something like:

  plot_style = case smooth do
    true -> if smoothed, do: :smooth, else: :direct
    _ -> style
  end

[larshei]

Adjusted to

    plot_style =
      case smoothed do
        true -> :smooth
        false -> :direct
        _ -> style
      end

[mindok]

Thanks @larshei - I've set aside some time to take a look on Monday. Apologies for the slow responses.