Write methods to calculate the periodicity of syllable sequence

Issue #370
QutEcoacoustics · Sep 3, 2020 · 6b1e478 · 6b1e478
1 parent fb753a8
commit 6b1e478
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diff --git a/src/AudioAnalysisTools/Events/EventExtentions.cs b/src/AudioAnalysisTools/Events/EventExtentions.cs
@@ -381,6 +381,36 @@ public static List<EventCommon> FilterEventsOnCompositeContent(
             return filteredEvents;
         }
 
+        /// <summary>
+        /// Removes composite events from a list of EventCommon where the component syllables do not have the correct periodicity.
+        /// </summary>
+        public static List<EventCommon> FilterEventsOnSyllablePeriodicity(
+            List<EventCommon> events,
+            double expectedPeriod,
+            double periodSd)
+        {
+            var filteredEvents = new List<EventCommon>();
+
+            foreach (var ev in events)
+            {
+                if (ev is CompositeEvent)
+                {
+                    var actualPeriodicity = ((CompositeEvent)ev).CalculatePeriodicity();
+                    var minAllowedPeriodicity = expectedPeriod - (3 * periodSd);
+                    var maxAllowedPeriodicity = expectedPeriod + (3 * periodSd);
+                    if (actualPeriodicity < minAllowedPeriodicity || actualPeriodicity > maxAllowedPeriodicity)
+                    {
+                        // ignore composite events which do not have the correct periodicity
+                        continue;
+                    }
+                }
+
+                filteredEvents.Add(ev);
+            }
+
+            return filteredEvents;
+        }
+
         /// <summary>
         /// Combines all the tracks in all the events in the passed list into a single track.
         /// Each frame in the composite event is assigned the spectral point having maximum amplitude.

diff --git a/src/AudioAnalysisTools/Events/Types/CompositeEvent.cs b/src/AudioAnalysisTools/Events/Types/CompositeEvent.cs
@@ -41,6 +41,22 @@ public CompositeEvent(List<SpectralEvent> events)
         public override double Score =>
             this.ComponentEvents.Max(x => (x as SpectralEvent)?.Score) ?? double.PositiveInfinity;
 
+        public double CalculatePeriodicity()
+        {
+            var eventStarts = new List<double>();
+            foreach (var ev in this.ComponentEvents)
+            {
+                eventStarts.Add(ev.EventStartSeconds);
+            }
+
+            // Sort array in ascending order.
+            var array = eventStarts.ToArray();
+            Array.Sort(array);
+            var periodicity = Math.Abs(array[0] - array[array.Length - 1]) / array.Length;
+
+            return periodicity;
+        }
+
         public IEnumerable<ITrack> Tracks
         {
             get