Begin statistics creation

CHDataManagement/Workouts/Sequence+Median.swift

@@ -9,6 +9,31 @@ private struct Entry<T: BinaryFloatingPoint>: Comparable {
 }
 
 extension Sequence {
+
+    func firstElement() -> Element? {
+        for element in self {
+            return element
+        }
+        return nil
+    }
+
+    func minMax<E>(by converting: (Element) -> E) -> (min: E, max: E)? where E: Comparable {
+        guard let first = firstElement() else {
+            return nil
+        }
+        var minimum = converting(first)
+        var maximum = minimum
+        for location in dropFirst() {
+            let value = converting(location)
+            if value < minimum {
+                minimum = value
+            } else if value > maximum {
+                maximum = value
+            }
+        }
+        return (minimum, maximum)
+    }
+
     /// Applies a centered median filter to the sequence.
     /// - Parameters:
     ///   - windowSize: The number of samples in the median filter window (should be odd for symmetric centering).