added convenience initializer

README.md

@@ -61,6 +61,10 @@ typealias MD = ModifiedDietz<Float>
 
 ## Initialization
 
+Two initializers are provided, one more explicit than the other, but functionally equivalent:
+
+- `init?(period: DateInterval, startValue: T, endValue: T, cashflowMap: [Date: T], epsilon: T)` - Conveniently initialize a ModifiedDietz with explicit parameters.
+
 - `init?(DateInterval, ModifiedDietz<T>.MarketValueDelta, ModifiedDietz<T>.CashflowMap, epsilon: T)` - Initialize a ModifiedDietz with the specified parameters.
 
 Initialization will fail and return `nil` if provided nonsense parameters, such as a period with zero duration.

Sources/ModifiedDietz.swift

@@ -44,6 +44,16 @@ public final class ModifiedDietz<T: BinaryFloatingPoint> {
     /// Optional precision for comparing values that are very close to one another.
     public let epsilon: T
 
+    /// Conveniently initialize a `ModifiedDietz` with explicit parameters.
+    public convenience init?(period: DateInterval,
+                             startValue: T,
+                             endValue: T,
+                             cashflowMap: CashflowMap = [:],
+                             epsilon: T = 0.0001) {
+        let mvd = MarketValueDelta(start: startValue, end: endValue)
+        self.init(period, mvd, cashflowMap, epsilon: epsilon)
+    }
+
     /// Initialize a `ModifiedDietz` with the specified parameters.
     public init?(_ period: DateInterval,
                  _ marketValue: MarketValueDelta,

Tests/ModifiedDietzTests.swift

@@ -238,4 +238,19 @@ final class MDTests: XCTestCase {
         XCTAssertEqual(0.05, md.performance, accuracy: 0.001)
         //print("\(md.performance * 100)%")
     }
+
+    func testConvenienceInit() throws {
+        typealias MD = ModifiedDietz<Double>
+        let df = ISO8601DateFormatter()
+        let beg = df.date(from: "2020-06-01T12:00:00Z")!
+        let mid = df.date(from: "2020-06-16T00:00:00Z")!
+        let end = df.date(from: "2020-06-30T12:00:00Z")!
+
+        let period = DateInterval(start: beg, end: end)
+        let cf: MD.CashflowMap = [mid: -10.0]
+        let md = MD(period: period, startValue: 105, endValue: 100, cashflowMap: cf)!
+
+        XCTAssertEqual(0.05, md.performance, accuracy: 0.001)
+        //print("\(md.performance * 100)%")
+    }
 }