Mjc/has gradual transitions (#23)

* Adds gradual transition validation for retrospective correction as a mitigation for spurious iCGM values

* Add gradualTransitionsThreshold to AlgorithmInput and related structures

Set RC transition check to only use the last 7 samples

* Refactor conditions in momentum to include gradual transitions check

* Changed default for gradualTransitionThreshold from 20 -> 40

* fixed naming for gradualTransitionThreshold

* Missed a name change on cleanup

* Add tests

* fix comma for older xcode

* Update xcode

* Update xcode version

* Change resource class

* Update simulator

---------

Co-authored-by: Pete Schwamb <pete@schwamb.net>

Author: markjudeconnolly

.circleci/config.yml

@@ -7,24 +7,26 @@ version: 2.1
 jobs:
   test:
     macos:
-      xcode: 16.0.0
+      xcode: 26.1.0
+    resource_class: m4pro.medium
     steps:
       - checkout
       - run:
           name: Test
           command: |
-            set -o pipefail && xcodebuild -scheme LoopAlgorithm test -destination "platform=iOS Simulator,name=iPhone 16,OS=latest" | xcpretty
+            set -o pipefail && xcodebuild -scheme LoopAlgorithm test -destination "platform=iOS Simulator,name=iPhone 17,OS=latest" | xcpretty
       - store_test_results:
           path: test_output
   package:
     macos:
-      xcode: 16.0.0
+      xcode: 26.1.0
+    resource_class: m4pro.medium
     steps:
       - checkout
       - run:
           name: Build LoopAlgorithmPackage
           command: |
-            set -o pipefail && xcodebuild build -scheme LoopAlgorithm -destination "platform=iOS Simulator,name=iPhone 16,OS=latest" | xcpretty
+            set -o pipefail && xcodebuild build -scheme LoopAlgorithm -destination "platform=iOS Simulator,name=iPhone 17,OS=latest" | xcpretty
 #
 # Workflows
 #

Sources/LoopAlgorithm/AlgorithmInput.swift

@@ -33,6 +33,5 @@ public protocol AlgorithmInput {
     var recommendationInsulinModel: InsulinModel { get }
     var recommendationType: DoseRecommendationType { get }
     var automaticBolusApplicationFactor: Double? { get } // Defaults to 0.4
+    var gradualTransitionsThreshold: Double? { get }
 }
-
-

Sources/LoopAlgorithm/AlgorithmInputFixture.swift

@@ -34,6 +34,7 @@ public struct AlgorithmInputFixture: AlgorithmInput {
     public var recommendationInsulinType: FixtureInsulinType = .novolog
     public var recommendationType: DoseRecommendationType = .automaticBolus
     public var automaticBolusApplicationFactor: Double?
+    public var gradualTransitionsThreshold: Double?
 
     public var recommendationInsulinModel: InsulinModel {
         recommendationInsulinType.insulinModel
@@ -71,7 +72,8 @@ public struct AlgorithmInputFixture: AlgorithmInput {
         carbAbsorptionModel: CarbAbsorptionModel = .piecewiseLinear,
         recommendationInsulinType: FixtureInsulinType,
         recommendationType: DoseRecommendationType,
-        automaticBolusApplicationFactor: Double? = nil
+        automaticBolusApplicationFactor: Double? = nil,
+        gradualTransitionsThreshold: Double? = 40.0
     ) {
         self.predictionStart = predictionStart
         self.glucoseHistory = glucoseHistory
@@ -92,6 +94,7 @@ public struct AlgorithmInputFixture: AlgorithmInput {
         self.recommendationInsulinType = recommendationInsulinType
         self.recommendationType = recommendationType
         self.automaticBolusApplicationFactor = automaticBolusApplicationFactor
+        self.gradualTransitionsThreshold = gradualTransitionsThreshold
     }
 }
 
@@ -144,6 +147,7 @@ extension AlgorithmInputFixture: Codable {
         }
 
         self.automaticBolusApplicationFactor = try container.decodeIfPresent(Double.self, forKey: .automaticBolusApplicationFactor)
+        self.gradualTransitionsThreshold = try container.decodeIfPresent(Double.self, forKey: .gradualTransitionsThreshold) ?? 40.0
 
     }
 
@@ -179,6 +183,7 @@ extension AlgorithmInputFixture: Codable {
         try container.encode(recommendationInsulinType.rawValue, forKey: .recommendationInsulinType)
         try container.encode(recommendationType.rawValue, forKey: .recommendationType)
         try container.encode(automaticBolusApplicationFactor, forKey: .automaticBolusApplicationFactor)
+        try container.encode(gradualTransitionsThreshold, forKey: .gradualTransitionsThreshold)
     }
 
     private enum CodingKeys: String, CodingKey {
@@ -200,6 +205,7 @@ extension AlgorithmInputFixture: Codable {
         case recommendationInsulinType
         case recommendationType
         case automaticBolusApplicationFactor
+        case gradualTransitionsThreshold
     }
 }
 
@@ -223,7 +229,8 @@ extension AlgorithmInputFixture {
             carbAbsorptionModel: input.carbAbsorptionModel,
             recommendationInsulinType: .novolog,
             recommendationType: input.recommendationType,
-            automaticBolusApplicationFactor: input.automaticBolusApplicationFactor
+            automaticBolusApplicationFactor: input.automaticBolusApplicationFactor,
+            gradualTransitionsThreshold: input.gradualTransitionsThreshold
         )
 
         let encoder = JSONEncoder()
@@ -261,4 +268,3 @@ extension CarbEntry {
         )
     }
 }
-

Sources/LoopAlgorithm/Glucose/GlucoseMath.swift

@@ -61,7 +61,7 @@ extension BidirectionalCollection where Element: GlucoseSampleValue, Index == In
     /// - Parameters:
     ///   - interval: The interval between readings, on average, used to determine if we have a contiguous set of values
     /// - Returns: True if the samples are continuous
-    public func isContinuous(within interval: TimeInterval = TimeInterval(5 * 60)) -> Bool {
+    func isContinuous(within interval: TimeInterval = TimeInterval(minutes: 5)) -> Bool {
         if  let first = first,
             let last = last,
             // Ensure that the entries are contiguous
@@ -73,6 +73,34 @@ extension BidirectionalCollection where Element: GlucoseSampleValue, Index == In
         return false
     }
 
+    /// Whether the collection has gradual transitions (no large glucose jumps between consecutive readings)
+    /// 
+    /// - Parameters:
+    ///   - gradualTransitionThreshold: Maximum allowed difference between consecutive readings in mg/dL (default 40.0)
+    /// - Returns: True if all consecutive differences are within the threshold
+    public func hasGradualTransitions(gradualTransitionThreshold: Double = 40.0) -> Bool {
+        guard count > 1 else {
+            return false  // A single point could be a spike and should not be used for momentum calculation
+        }
+
+        // Check glucose value continuity (no large transitions)
+        let unit = LoopUnit.milligramsPerDeciliter
+        for i in 0..<(count - 1) {
+            let current = self[self.index(self.startIndex, offsetBy: i)]
+            let next = self[self.index(self.startIndex, offsetBy: i + 1)]
+
+            let currentValue = current.quantity.doubleValue(for: unit)
+            let nextValue = next.quantity.doubleValue(for: unit)
+            let difference = abs(nextValue - currentValue)
+
+            if difference > gradualTransitionThreshold {
+                return false
+            }
+        }
+
+        return true
+    }
+
     /// Calculates the short-term predicted momentum effect using linear regression
     ///
     /// - Parameters:
@@ -90,7 +118,7 @@ extension BidirectionalCollection where Element: GlucoseSampleValue, Index == In
 
         guard
             self.count > 2,  // Linear regression isn't much use without 3 or more entries.
-            isContinuous() && !containsCalibrations() && hasSingleProvenance,
+            hasGradualTransitions() && isContinuous() && !containsCalibrations() && hasSingleProvenance,
             let firstSample = self.first,
             let lastSample = self.last,
             let (startDate, endDate) = LoopMath.simulationDateRangeForSamples([lastSample], duration: duration, delta: delta)

Sources/LoopAlgorithm/LoopAlgorithm.swift

@@ -178,7 +178,8 @@ public struct LoopAlgorithm {
         useIntegralRetrospectiveCorrection: Bool = false,
         includingPositiveVelocityAndRC: Bool = true,
         useMidAbsorptionISF: Bool = false,
-        carbAbsorptionModel: CarbAbsorptionComputable = PiecewiseLinearAbsorption()
+        carbAbsorptionModel: CarbAbsorptionComputable = PiecewiseLinearAbsorption(),
+        gradualTransitionsThreshold: Double? = 40.0
     ) -> LoopPrediction<CarbType> where CarbType: CarbEntry, GlucoseType: GlucoseSampleValue, InsulinDoseType: InsulinDose {
 
         var prediction: [PredictedGlucoseValue] = []
@@ -259,8 +260,6 @@ public struct LoopAlgorithm {
             rc = StandardRetrospectiveCorrection(effectDuration: LoopMath.retrospectiveCorrectionEffectDuration)
         }
 
-        
-
         if let latestGlucose = glucoseHistory.last {
             retrospectiveCorrectionEffects = rc.computeEffect(
                 startingAt: latestGlucose,
@@ -282,9 +281,28 @@ public struct LoopAlgorithm {
             }
 
             if algorithmEffectsOptions.contains(.retrospection) {
-                if !includingPositiveVelocityAndRC, let netRC = retrospectiveCorrectionEffects.netEffect(), netRC.quantity.doubleValue(for: .milligramsPerDeciliter) > 0 {
-                    // positive RC is turned off
-                } else {
+                // Check if glucose data is smooth enough for RC
+                // Use the same input window as retrospective correction             
+                var useRC: Bool = true
+
+                // Don't apply RC if glucose has large jumps
+                let rcTransitionData = glucoseHistory.filterDateRange(
+                    start.addingTimeInterval(-LoopMath.retrospectiveCorrectionGroupingInterval), 
+                    start
+                )   
+
+                if !rcTransitionData.hasGradualTransitions(gradualTransitionThreshold: gradualTransitionsThreshold ?? 40.0) {
+                    useRC = false
+                }
+
+                // Don't apply positive RC if that setting is disabled
+                if !includingPositiveVelocityAndRC, 
+                    let netRC = retrospectiveCorrectionEffects.netEffect(), 
+                    netRC.quantity.doubleValue(for: .milligramsPerDeciliter) > 0 {
+                        useRC = false
+                    }
+                
+                if useRC {
                     effects.append(retrospectiveCorrectionEffects)
                 }
             }
@@ -347,7 +365,8 @@ public struct LoopAlgorithm {
             carbRatio: input.carbRatio,
             algorithmEffectsOptions: input.algorithmEffectsOptions,
             useIntegralRetrospectiveCorrection: input.useIntegralRetrospectiveCorrection,
-            carbAbsorptionModel: input.carbAbsorptionModel.model
+            carbAbsorptionModel: input.carbAbsorptionModel.model,
+            gradualTransitionsThreshold: input.gradualTransitionsThreshold
         )
     }
 
@@ -530,7 +549,8 @@ public struct LoopAlgorithm {
                 useIntegralRetrospectiveCorrection: input.useIntegralRetrospectiveCorrection,
                 includingPositiveVelocityAndRC: input.includePositiveVelocityAndRC,
                 useMidAbsorptionISF: input.useMidAbsorptionISF,
-                carbAbsorptionModel: input.carbAbsorptionModel.model
+                carbAbsorptionModel: input.carbAbsorptionModel.model,
+                gradualTransitionsThreshold: input.gradualTransitionsThreshold
             )
 
             let sensitivityForDosing: [AbsoluteScheduleValue<LoopQuantity>]
@@ -600,4 +620,3 @@ public struct LoopAlgorithm {
         )
     }
 }
-

Sources/LoopAlgorithm/LoopPredictionInput.swift

@@ -34,6 +34,8 @@ public struct LoopPredictionInput<CarbType: CarbEntry, GlucoseType: GlucoseSampl
     public var includePositiveVelocityAndRC: Bool = true
 
     public var carbAbsorptionModel: CarbAbsorptionModel = .piecewiseLinear
+    
+    public var gradualTransitionsThreshold: Double? = 40.0
 
     public init(
         glucoseHistory: [GlucoseType],
@@ -45,7 +47,8 @@ public struct LoopPredictionInput<CarbType: CarbEntry, GlucoseType: GlucoseSampl
         algorithmEffectsOptions: AlgorithmEffectsOptions,
         useIntegralRetrospectiveCorrection: Bool,
         includePositiveVelocityAndRC: Bool,
-        carbAbsorptionModel: CarbAbsorptionModel
+        carbAbsorptionModel: CarbAbsorptionModel,
+        gradualTransitionsThreshold: Double? = 40.0
     )
     {
         self.glucoseHistory = glucoseHistory
@@ -58,6 +61,7 @@ public struct LoopPredictionInput<CarbType: CarbEntry, GlucoseType: GlucoseSampl
         self.useIntegralRetrospectiveCorrection = useIntegralRetrospectiveCorrection
         self.includePositiveVelocityAndRC = includePositiveVelocityAndRC
         self.carbAbsorptionModel = carbAbsorptionModel
+        self.gradualTransitionsThreshold = gradualTransitionsThreshold
     }
 }
 
@@ -81,6 +85,7 @@ extension LoopPredictionInput: Codable where CarbType == FixtureCarbEntry, Gluco
         self.useIntegralRetrospectiveCorrection = try container.decodeIfPresent(Bool.self, forKey: .useIntegralRetrospectiveCorrection) ?? false
         self.includePositiveVelocityAndRC = try container.decodeIfPresent(Bool.self, forKey: .includePositiveVelocityAndRC) ?? true
         self.carbAbsorptionModel = try container.decodeIfPresent(CarbAbsorptionModel.self, forKey: .carbAbsorptionModel) ?? .piecewiseLinear
+        self.gradualTransitionsThreshold = try container.decodeIfPresent(Double.self, forKey: .gradualTransitionsThreshold) ?? 40.0
 
     }
 
@@ -103,6 +108,7 @@ extension LoopPredictionInput: Codable where CarbType == FixtureCarbEntry, Gluco
             try container.encode(includePositiveVelocityAndRC, forKey: .includePositiveVelocityAndRC)
         }
         try container.encode(carbAbsorptionModel, forKey: .carbAbsorptionModel)
+        try container.encode(gradualTransitionsThreshold, forKey: .gradualTransitionsThreshold)
     }
 
     private enum CodingKeys: String, CodingKey {
@@ -116,5 +122,6 @@ extension LoopPredictionInput: Codable where CarbType == FixtureCarbEntry, Gluco
         case useIntegralRetrospectiveCorrection
         case includePositiveVelocityAndRC
         case carbAbsorptionModel
+        case gradualTransitionsThreshold
     }
 }