Splitting Observable into windows

Question

I am looking for Observable.Window like operator with opening window selector

As example we can take a sequence of natural numbers. I am wondering how to split this sequence into windows so every new window starts if number is greater than 4 or window size has reached 3

Input sequence is IObservable<int> Output sequence is IObservable<IObservable<int>>

Sequence 1 2 5 3 1 1 2 3 1 5 0 will produce windows 1 2; 5 3 1; 1 2 3; 1; 5 0

Should `1, 2, 3, 5` produce the windows `1 2 3; 5` or `1 2 3; ; 5`? (Notice the empty window) — Lukazoid, Feb 29 '16 at 00:28
Sorry for not making it clear ';' - was a separator between desired sequences — bublegumm, Mar 01 '16 at 03:34
I understand that, but run both answers with the input sequence 1,2,3,5 and they produce different results. — Lukazoid, Mar 01 '16 at 09:52

score 3 · Accepted Answer · answered Feb 27 '16 at 01:39

3

Using C# this works:

var observable =
    source
        .Concat(Observable.Return(-1))
        .Publish(sp =>
            sp.Zip(sp.Skip(1), (x0, x1) => new { x0, x1 })
                .Publish(zsp =>
                    zsp
                        .Window(zsp.Where(x => x.x1 >= 4))
                        .Select(xs => xs.Select(x => x.x0).Window(3))
                        .Merge()));

I get this result:

answered Feb 27 '16 at 01:39

Enigmativity

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what is the tool you use for visualizing `Observable` results ? – supertopi Mar 01 '16 at 11:48

score 1 · Answer 2 · answered Feb 29 '16 at 00:31

As per my comment on the question I am unsure whether the sequence 1, 2, 3, 5 should produce the windows 1 2 3 | 5 or 1 2 3 | | 5 (see the empty window which is what Enigmativity's answer produces). My answer does not produce the empty window:

public static IObservable<IObservable<T>> Window<T>(this IObservable<T> source, Func<T, bool> predicate, int maximumWindowSize)
{
    return Observable.Create<IObservable<T>>(obs =>
    {
        var currentWindow = new Subject<T>();
        obs.OnNext(currentWindow);

        var count = 0;

        return source.Subscribe(x =>
        {
            if (count == maximumWindowSize || predicate(x))
            {
                count = 0;
                currentWindow.OnCompleted();
                currentWindow = new Subject<T>();
                obs.OnNext(currentWindow);
            }
            currentWindow.OnNext(x);
            count++;
        }, obs.OnError, () =>
        {
            obs.OnCompleted();
            currentWindow.OnCompleted();
        });
    });
}

This can be used like so:

var windows = source.Window(x => x > 4, 3);

I tested mine and didn't get the empty result in the middle. Can you post the code you used to test my code? — Enigmativity, Mar 01 '16 at 07:05

Splitting Observable into windows

2 Answers2