median of medians

ledger/predict.go

@@ -80,17 +80,29 @@ func registerWithContributionPredictionForNameForCurrency(reg Register, window t
 		if wouldBe == 0 {
 			wouldBe = 2
 		}
-		return contributions[len(contributions)-wouldBe:]
+		return contributions[len(contributions)-1-wouldBe:]
 	}
 
 	eighth := contributsSlice(7.0 / 8.0)
 	quarter := contributsSlice(3.0 / 4.0)
 	half := contributsSlice(1.0 / 2.0)
 	medianValueDelta := func() float64 {
-		return (4.0*getMedianValueDelta(eighth) + 2.0*getMedianValueDelta(quarter) + 1.0*getMedianValueDelta(half)) / (4.0 + 2.0 + 1.0)
+		medians := []float64{
+			getMedianValueDelta(eighth),
+			getMedianValueDelta(quarter),
+			getMedianValueDelta(half),
+		}
+		slices.Sort(medians)
+		return medians[1]
 	}()
 	medianLapse := func() time.Duration {
-		return (4.0*getMedianLapse(eighth) + 2.0*getMedianLapse(quarter) + 1.0*getMedianLapse(half)) / (4.0 + 2.0 + 1.0)
+		medians := []time.Duration{
+			getMedianLapse(eighth),
+			getMedianLapse(quarter),
+			getMedianLapse(half),
+		}
+		slices.Sort(medians)
+		return medians[1]
 	}()
 
 	latest := func() float64 {