mirror of https://github.com/ppy/osu
38 lines
1.5 KiB
C#
38 lines
1.5 KiB
C#
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// Copyright (c) ppy Pty Ltd <contact@ppy.sh>. Licensed under the MIT Licence.
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// See the LICENCE file in the repository root for full licence text.
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using System;
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using System.Collections.Generic;
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using System.Linq;
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namespace osu.Game.Rulesets.Scoring
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{
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public static class HitEventExtensions
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{
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/// <summary>
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/// Calculates the "unstable rate" for a sequence of <see cref="HitEvent"/>s.
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/// </summary>
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/// <returns>
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/// A non-null <see langword="double"/> value if unstable rate could be calculated,
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/// and <see langword="null"/> if unstable rate cannot be calculated due to <paramref name="hitEvents"/> being empty.
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/// </returns>
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public static double? CalculateUnstableRate(this IEnumerable<HitEvent> hitEvents)
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{
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double[] timeOffsets = hitEvents.Where(affectsUnstableRate).Select(ev => ev.TimeOffset).ToArray();
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return 10 * standardDeviation(timeOffsets);
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}
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private static bool affectsUnstableRate(HitEvent e) => !(e.HitObject.HitWindows is HitWindows.EmptyHitWindows) && e.Result.IsHit();
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private static double? standardDeviation(double[] timeOffsets)
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{
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if (timeOffsets.Length == 0)
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return null;
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double mean = timeOffsets.Average();
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double squares = timeOffsets.Select(offset => Math.Pow(offset - mean, 2)).Sum();
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return Math.Sqrt(squares / timeOffsets.Length);
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}
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}
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}
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