Update Variance and StdDev Indicators to modern syntax

Author: sdcoffey

indicator_standard_deviation.go

@@ -4,15 +4,19 @@ import (
 	"github.com/sdcoffey/big"
 )
 
-// StandardDeviationIndicator calculates the standard deviation of a base indicator.
+// NewStandardDeviationIndicator calculates the standard deviation of a base indicator.
 // See https://www.investopedia.com/terms/s/standarddeviation.asp
-type StandardDeviationIndicator struct {
-	Indicator Indicator
+func NewStandardDeviationIndicator(ind Indicator) Indicator {
+	return standardDeviationIndicator{
+		indicator: NewVarianceIndicator(ind),
+	}
+}
+
+type standardDeviationIndicator struct {
+	indicator Indicator
 }
 
 // Calculate returns the standard deviation of a base indicator
-func (sdi StandardDeviationIndicator) Calculate(index int) big.Decimal {
-	return VarianceIndicator{
-		Indicator: sdi.Indicator,
-	}.Calculate(index).Sqrt()
+func (sdi standardDeviationIndicator) Calculate(index int) big.Decimal {
+	return sdi.indicator.Calculate(index).Sqrt()
 }

indicator_standard_deviation_test.go

@@ -9,9 +9,7 @@ import (
 func TestStandardDeviationIndicator(t *testing.T) {
 	t.Run("when index is less than 1, returns 0", func(t *testing.T) {
 		series := mockTimeSeries("0", "10")
-		stdDev := StandardDeviationIndicator{
-			Indicator: NewClosePriceIndicator(series),
-		}
+		stdDev := NewStandardDeviationIndicator(NewClosePriceIndicator(series))
 
 		assert.EqualValues(t, "0", stdDev.Calculate(0).String())
 	})
@@ -26,9 +24,7 @@ func TestStandardDeviationIndicator(t *testing.T) {
 			23,
 			21)
 
-		stdDev := StandardDeviationIndicator{
-			Indicator: NewClosePriceIndicator(series),
-		}
+		stdDev := NewStandardDeviationIndicator(NewClosePriceIndicator(series))
 
 		assert.EqualValues(t, "4.00", stdDev.Calculate(1).FormattedString(2))
 		assert.EqualValues(t, "15.43", stdDev.Calculate(2).FormattedString(2))

indicator_variance.go

@@ -2,14 +2,20 @@ package techan
 
 import "github.com/sdcoffey/big"
 
-// VarianceIndicator provides a way to find the variance in a base indicator, where variances is the sum of squared
+// NewVarianceIndicator provides a way to find the variance in a base indicator, where variances is the sum of squared
 // deviations from the mean at any given index in the time series.
-type VarianceIndicator struct {
+func NewVarianceIndicator(ind Indicator) Indicator {
+	return varianceIndicator{
+		Indicator: ind,
+	}
+}
+
+type varianceIndicator struct {
 	Indicator Indicator
 }
 
 // Calculate returns the Variance for this indicator at the given index
-func (vi VarianceIndicator) Calculate(index int) big.Decimal {
+func (vi varianceIndicator) Calculate(index int) big.Decimal {
 	if index < 1 {
 		return big.ZERO
 	}

indicator_variance_test.go

@@ -9,9 +9,7 @@ import (
 func TestVarianceIndicator(t *testing.T) {
 	t.Run("when index is less than 1, returns 0", func(t *testing.T) {
 		series := mockTimeSeries("0", "10")
-		stdDev := StandardDeviationIndicator{
-			Indicator: NewClosePriceIndicator(series),
-		}
+		stdDev := NewStandardDeviationIndicator(NewClosePriceIndicator(series))
 
 		assert.EqualValues(t, "0", stdDev.Calculate(0).String())
 	})
@@ -26,15 +24,13 @@ func TestVarianceIndicator(t *testing.T) {
 			23,
 			21)
 
-		stdDev := VarianceIndicator{
-			Indicator: NewClosePriceIndicator(series),
-		}
+		varInd := NewVarianceIndicator(NewClosePriceIndicator(series))
 
-		assert.EqualValues(t, "16.00", stdDev.Calculate(1).FormattedString(2))
-		assert.EqualValues(t, "238.22", stdDev.Calculate(2).FormattedString(2))
-		assert.EqualValues(t, "186.19", stdDev.Calculate(3).FormattedString(2))
-		assert.EqualValues(t, "211.36", stdDev.Calculate(4).FormattedString(2))
-		assert.EqualValues(t, "176.22", stdDev.Calculate(5).FormattedString(2))
-		assert.EqualValues(t, "151.27", stdDev.Calculate(6).FormattedString(2))
+		assert.EqualValues(t, "16.00", varInd.Calculate(1).FormattedString(2))
+		assert.EqualValues(t, "238.22", varInd.Calculate(2).FormattedString(2))
+		assert.EqualValues(t, "186.19", varInd.Calculate(3).FormattedString(2))
+		assert.EqualValues(t, "211.36", varInd.Calculate(4).FormattedString(2))
+		assert.EqualValues(t, "176.22", varInd.Calculate(5).FormattedString(2))
+		assert.EqualValues(t, "151.27", varInd.Calculate(6).FormattedString(2))
 	})
 }

timeseries.go

@@ -21,7 +21,7 @@ func NewTimeSeries() (t *TimeSeries) {
 // If the candle is added, AddCandle will return true, otherwise it will return false.
 func (ts *TimeSeries) AddCandle(candle *Candle) bool {
 	if candle == nil {
-		panic(fmt.Errorf("Error adding Candle: candle cannot be nil"))
+		panic(fmt.Errorf("error adding Candle: candle cannot be nil"))
 	}
 
 	if ts.LastCandle() == nil || candle.Period.Since(ts.LastCandle().Period) >= 0 {