Incorrect implementation of `scaleXTime()`/`scaleYTime()` "time delta" scales

[Jolanrensen]

Let's plot allows an axis to be scaled as a continuous time delta or "duration".
I currently cannot find a way to easily plot a Duration like a number of hours/days/minutes etc.

For example:
https://nbviewer.org/github/JetBrains/lets-plot-kotlin/blob/master/docs/examples/jupyter-notebooks/scale_time.ipynb

from: https://github.com/JetBrains/lets-plot-kotlin/blob/master/plot-api/src/commonMain/kotlin/org/jetbrains/letsPlot/scale/DateTime.kt

[Jolanrensen]

Oh actually, I see scaleXTime() is used in Kandy, but only for timeTypes (LocalTime and LocalTime?).

That may be incorrect usage, actually. I think scaleXDateTime is used for points in time, so Instant, LocalDateTime, but also LocalTime, and then scaleXTime is used for time deltas, so Duration or number of milliseconds.

[AndreiKingsley]

So basically you want kandy to handle Duration in the same way as LocalTime/LocalDateTime?

[Jolanrensen]

Yes and no:

• Instant, LocalDateTime, and LocalTime should use scaleXDateTime.
• Duration, and Period should use scaleXTime

[AndreiKingsley]

Hmm, I guess you're right. I need to do a little research and see if it works correctly, but in terms of implementation it won't be resource intensive at all - just need to take milliseconds value of your duration/period and apply scaleTime().

[gj-honey]

Is there a chance we could see an example of how to apply this with the Kandy API? The notebook above uses letsPlot directly.
(i'm trying to plot a Duration on the Y axis and without doing any conversion, it just seems to default to a categorical scale using the toString value of the duration - converting to (milli)seconds is trivial, but the axis/legend/labels need the inverse conversion again, which is a bit yuk)

[AndreiKingsley]

@gj-honey, hi! The issue with the Duration has not yet been resolved. Unfortunately, you can't use it for now, but I'll address this issue in the next release.

For now the only workaround is a converting to Lets-Plot and applying scaleTime from Lets-plot API manually:

plot {
    line {
        x(durations.map { it.inWholeMilliseconds })
        y(listOf(1, 2, 3))
    }
}.toLetsPlot() + scaleXTime()

As you can see, Lets-Plot doesn't support Duration directly, but Kandy will do!

[gj-honey]

ha, thanks for that @AndreiKingsley , i'll try that workaround asap :)