Add functions to convert between jagged arrays and frames

[kMutagene]

Content

This PR adds functions to:

• Create frames from jagged arrays:
  • FromJaggedArray for C#, ofJaggedArray for F#
• Convert frames to jagged arrays:
  • static members toJaggedArray<'R> for any type of conversion for the frame data (returns 'R[][])
  • function Frame.toJaggedArray to return a float [][] analogously to Frame.ToArray2D
• I also added tests the same way they work for the Array2D functions, as well as a test that compares frames from an Array2D and a jagged array with the same data.

Why?

These are simply convenience functions that improve interop with Plotly.NET. I often handle data frames with numeric values only, where i want to visualize the contents after some transformations with Deedle. Charts that accept two-dimensional data in Plotly.NET expect data as jagged arrays, so i would love to see this added as it prevents a clunky conversion step from the Array2D obtained by Frame.ToArray2D and the chart initialization.

additional notes

The build fails for me with an outdated log format, so i updated build dependencies and fake as well, if that breaks anything please let me know.

[FoggyFinder]

creating a frame like that doesn't look effective . We create a copy of array just to pass it further? We can easily do the same even now

jArray |> array2D |> Frame.FromArray2D

[kMutagene]

I was not thinking about performance here, as I see the frame creation as a step that only happens a single time in a data analysis pipeline, but i can definitely adjust this to work exactly as the FromArray2D function.

We can easily do the same even now
jArray |> array2D |> Frame.FromArray2D

Agreed, but the whole point of this PR is to get rid of the function in the middle. And where is the array2D from this example coming from anyways? I cant find it in FSharp.Core and needing an external library for that or having to do the copy in the analysis is exactly what i want to prevent.

[FoggyFinder]

And where is the array2D from this example coming from anyways

that's from FSharp.Core

https://github.com/dotnet/fsharp/blob/dbf9a625d3188184ecb787a536ddb85a4ea7a587/src/fsharp/FSharp.Core/fslib-extra-pervasives.fs#L185-L204

[kMutagene]

Well that was a brainfart on my side :D sorry.

[kMutagene]

I used the same code now that is used in FromArray2D so I think it should be now more performant either way

[zyzhu]

It's indeed a convenience function, especially from C# as there is no helper function array2D in C#. Thanks for your review @FoggyFinder!

[zyzhu]

@kMutagene, I've released 2.4.1. BTW, would you like to be a co-maintainer of this project? As you are the main contributor to FsLab ecosystem, it could help you to iterate faster.

[kMutagene]

@zyzhu sure, that would be great!

[zyzhu]

That's great! Just added you as maintainer of the project now. I also sent you invitation on nuget.