feat: Added Smooting extension method.

mathrunet · Dec 4, 2023 · e474c9a · e474c9a
1 parent 2169a84
commit e474c9a
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Showing 4 changed files with 68 additions and 0 deletions.
diff --git a/packages/katana/lib/extension/double_iterable_extensions.dart b/packages/katana/lib/extension/double_iterable_extensions.dart
@@ -123,4 +123,34 @@ extension DoubleIterableExtensions on Iterable<double> {
     }
     return reduce((a, b) => a < b ? a : b);
   }
+
+  /// Smooth this array with [n] moving averages.
+  ///
+  /// [n] must be an odd number.
+  ///
+  /// この配列を[n]個の移動平均で平滑化します。
+  ///
+  /// [n]は奇数である必要があります。
+  List<double> smoothing({int n = 3}) {
+    assert(3 % 2 == 1, "n must be odd number");
+    final array = toList();
+    final halfN = (n / 2).floor();
+    final result = <double>[];
+    for (int i = 0; i < array.length; i++) {
+      int start = i - halfN;
+      int end = i + halfN;
+      if (start < 0) {
+        start = 0;
+      }
+      if (end >= array.length) {
+        end = array.length - 1;
+      }
+      double sum = 0;
+      for (int j = start; j <= end; j++) {
+        sum += array[j];
+      }
+      result.add(sum / (end - start + 1));
+    }
+    return result;
+  }
 }
diff --git a/packages/katana/lib/extension/int_iterable_extensions.dart b/packages/katana/lib/extension/int_iterable_extensions.dart
@@ -123,4 +123,34 @@ extension IntIterableExtensions on Iterable<int> {
     }
     return reduce((a, b) => a < b ? a : b);
   }
+
+  /// Smooth this array with [n] moving averages.
+  ///
+  /// [n] must be an odd number.
+  ///
+  /// この配列を[n]個の移動平均で平滑化します。
+  ///
+  /// [n]は奇数である必要があります。
+  List<double> smoothing({int n = 3}) {
+    assert(3 % 2 == 1, "n must be odd number");
+    final array = toList();
+    final halfN = (n / 2).floor();
+    final result = <double>[];
+    for (int i = 0; i < array.length; i++) {
+      int start = i - halfN;
+      int end = i + halfN;
+      if (start < 0) {
+        start = 0;
+      }
+      if (end >= array.length) {
+        end = array.length - 1;
+      }
+      double sum = 0;
+      for (int j = start; j <= end; j++) {
+        sum += array[j];
+      }
+      result.add(sum / (end - start + 1));
+    }
+    return result;
+  }
 }
diff --git a/packages/katana/test/double_iterable_extensions_test.dart b/packages/katana/test/double_iterable_extensions_test.dart
@@ -39,4 +39,8 @@ void main() {
     final doubles = [1.0, 2.0, 3.0, 4.0];
     expect(doubles.standardDeviation(), 1.118033988749895);
   });
+  test("DoubleIterableExtensions.smoothing", () {
+    final doubles = [1.0, 9.0, 5.0, 4.0, 3.0];
+    expect(doubles.smoothing(), [5.0, 5.0, 6.0, 4.0, 3.5]);
+  });
 }
diff --git a/packages/katana/test/int_iterable_extensions_test.dart b/packages/katana/test/int_iterable_extensions_test.dart
@@ -39,4 +39,8 @@ void main() {
     final ints = [1, 2, 3, 4];
     expect(ints.standardDeviation(), 1.118033988749895);
   });
+  test("IntIterableExtensions.smoothing", () {
+    final ints = [1, 9, 5, 4, 3];
+    expect(ints.smoothing(), [5, 5, 6, 4, 3.5]);
+  });
 }