started TimeSeriesAlgebra

kmath-stat/src/commonMain/kotlin/space/kscience/kmath/series/SeriesAlgebra.kt

@@ -155,17 +155,6 @@ public class SeriesAlgebra<T, out A : Ring<T>, out BA : BufferAlgebra<T, A>, L>(
         return accumulator
     }
 
-    // TODO: add fold with recorded accumulation
-//    public inline fun <R> Buffer<T>.traceFold(initial: R, operation: A.(acc: R, T) -> R): Buffer<R> {
-//        var tempBuffer = elementAlgebra.bufferFactory(this.size) {i -> getAbsolute(i)}
-//        var accumulator = initial
-//        for (index in this.indices) {
-//            accumulator = elementAlgebra.operation(accumulator, getAbsolute(index))
-//            tempBuffer.set(index, accumulator)
-//        }
-//        return elementAlgebra.bufferFactory(this.size) {i -> tempBuffer.getAbsolute(i)}
-//    }
-
     public inline fun <R> Buffer<T>.foldWithLabel(initial: R, operation: A.(acc: R, arg: T, label: L) -> R): R {
         val labels = labels
         var accumulator = initial

kmath-stat/src/commonMain/kotlin/space/kscience/kmath/series/TimeSeriesAlgebra.kt

@@ -0,0 +1,37 @@
+/*
+ * Copyright 2018-2023 KMath contributors.
+ * Use of this source code is governed by the Apache 2.0 license that can be found in the license/LICENSE.txt file.
+ */
+
+package space.kscience.kmath.series
+
+import space.kscience.kmath.structures.Buffer
+
+
+
+public interface TimeSeries<R, T>: Series<R> {
+    public override val origin: Buffer<R>
+    public override val position: Int
+
+    // TODO: Specify the types of DateTime that can be contained in timeStamp Buffer
+    public val timeStamp: Buffer<T> // Buffer of some datetime instances like: Instant, LocalDate, LocalTime...
+}
+
+private class TimeSeriesImpl<R, T>(
+    override val origin: Buffer<R>,
+    override val timeStamp: Buffer<T>,
+    override val position: Int,
+    override val size: Int = origin.size,
+) : TimeSeries<R, T> by origin { // TODO: manage with delegation
+
+    init {
+        require(size > 0) { "Size must be positive" }
+        require(size <= origin.size) { "Slice size is larger than the original buffer" }
+        require(size <= timeStamp.size) { "Slice size is larger than the timeStamp buffer" }
+    }
+
+//    override fun toString(): String = "$origin-->${position}"
+}
+
+
+// TODO: add conversion to Buffer of Pairs ?