From b546d13fc47209e3a555539160b3cd79b5477cb7 Mon Sep 17 00:00:00 2001
From: "Michael J. Roberts" <84131395+michealroberts@users.noreply.github.com>
Date: Sun, 17 Dec 2023 15:32:29 +0000
Subject: [PATCH] feat: Added NewHyperbolicVCurve() *VCurveParams to vcurve
 IRIS module. Includes associated test suite for expected output and API
 struct definitions.

feat: Added NewHyperbolicVCurve() *VCurveParams to vcurve IRIS module. Includes associated test suite for expected output and API struct definitions.
---
 go.mod                    |  7 +++++
 go.sum                    |  6 ++++
 pkg/vcurve/vcurve.go      | 44 ++++++++++++++++++++++++++++
 pkg/vcurve/vcurve_test.go | 60 +++++++++++++++++++++++++++++++++++++++
 4 files changed, 117 insertions(+)
 create mode 100644 go.sum
 create mode 100644 pkg/vcurve/vcurve_test.go

diff --git a/go.mod b/go.mod
index 652a33a..cd40fbb 100644
--- a/go.mod
+++ b/go.mod
@@ -1,3 +1,10 @@
 module github.com/observerly/iris
 
 go 1.19
+
+require gonum.org/v1/gonum v0.14.0
+
+require (
+	golang.org/x/exp v0.0.0-20230321023759-10a507213a29 // indirect
+	golang.org/x/tools v0.7.0 // indirect
+)
diff --git a/go.sum b/go.sum
new file mode 100644
index 0000000..61dc257
--- /dev/null
+++ b/go.sum
@@ -0,0 +1,6 @@
+golang.org/x/exp v0.0.0-20230321023759-10a507213a29 h1:ooxPy7fPvB4kwsA2h+iBNHkAbp/4JxTSwCmvdjEYmug=
+golang.org/x/exp v0.0.0-20230321023759-10a507213a29/go.mod h1:CxIveKay+FTh1D0yPZemJVgC/95VzuuOLq5Qi4xnoYc=
+golang.org/x/tools v0.7.0 h1:W4OVu8VVOaIO0yzWMNdepAulS7YfoS3Zabrm8DOXXU4=
+golang.org/x/tools v0.7.0/go.mod h1:4pg6aUX35JBAogB10C9AtvVL+qowtN4pT3CGSQex14s=
+gonum.org/v1/gonum v0.14.0 h1:2NiG67LD1tEH0D7kM+ps2V+fXmsAnpUeec7n8tcr4S0=
+gonum.org/v1/gonum v0.14.0/go.mod h1:AoWeoz0becf9QMWtE8iWXNXc27fK4fNeHNf/oMejGfU=
diff --git a/pkg/vcurve/vcurve.go b/pkg/vcurve/vcurve.go
index 6be55db..ebaf932 100644
--- a/pkg/vcurve/vcurve.go
+++ b/pkg/vcurve/vcurve.go
@@ -1,5 +1,12 @@
 package vcurve
 
+import (
+	"math"
+
+	"gonum.org/v1/gonum/floats"
+	"gonum.org/v1/gonum/stat"
+)
+
 // Point is a data point with x and y coordinates.
 type Point struct {
 	x float64
@@ -20,3 +27,40 @@ type VCurveParams struct {
 	x []float64
 	y []float64
 }
+
+/*
+NewHyperbolicVCurve
+
+Creates a new VCurve object ready for applying the Levenberg-Marquardt iterative optimization technique.
+
+The VCurve object is initialized with the data points, and initial guesses for the parameters are calculated from the input data.
+*/
+func NewHyperbolicVCurve(data VCurve) *VCurveParams {
+	// Preallocate slices with the exact required capacity
+	dataX := make([]float64, 0, len(data.Points))
+	dataY := make([]float64, 0, len(data.Points))
+
+	// A single loop to populate the slices
+	for _, point := range data.Points {
+		dataX = append(dataX, point.x)
+		dataY = append(dataY, point.y)
+	}
+
+	// Get the initial guess for the parameter, for A, we take the mean value of the yData:
+	A := stat.Mean(dataY, nil)
+
+	// Get the initial guess for B, for B, we take the min value of the yData:
+	B := floats.Min(dataY)
+
+	// Get the initial guess for C, for C, we take the mean value of the xData:
+	C := stat.Mean(dataX, nil)
+
+	return &VCurveParams{
+		A: math.Round(A),
+		B: B,
+		C: C,
+		D: 0,
+		x: dataX,
+		y: dataY,
+	}
+}
diff --git a/pkg/vcurve/vcurve_test.go b/pkg/vcurve/vcurve_test.go
new file mode 100644
index 0000000..d8fc11c
--- /dev/null
+++ b/pkg/vcurve/vcurve_test.go
@@ -0,0 +1,60 @@
+package vcurve
+
+import (
+	"testing"
+)
+
+var (
+	points = []Point{
+		{x: 29000, y: 40.5},
+		{x: 29100, y: 36.2},
+		{x: 29200, y: 31.4},
+		{x: 29300, y: 28.6},
+		{x: 29400, y: 23.1},
+		{x: 29500, y: 21.2},
+		{x: 29600, y: 16.6},
+		{x: 29700, y: 13.7},
+		{x: 29800, y: 6.21},
+		{x: 29900, y: 4.21},
+		{x: 30000, y: 3.98},
+		{x: 30100, y: 4.01},
+		{x: 30200, y: 4.85},
+		{x: 30300, y: 11.1},
+		{x: 30400, y: 15.3},
+		{x: 30500, y: 22.1},
+		{x: 30600, y: 21.9},
+		{x: 30700, y: 27.4},
+		{x: 30800, y: 32.1},
+		{x: 30900, y: 36.5},
+		{x: 31000, y: 39.7},
+	}
+)
+
+func TestNewHyperbolicVCurve(t *testing.T) {
+	v := NewHyperbolicVCurve(VCurve{
+		Points: points,
+	})
+
+	// Deconstruct the VCurveParams struct
+	a, b, c, d := v.A, v.B, v.C, v.D
+
+	// Expect the initial guess for A to be the mean value of the yData:
+	if a != 21 {
+		t.Errorf("A should be 21, but got %v", a)
+	}
+
+	// Expect the initial guess for B to be the min value of the yData:
+	if b != 3.98 {
+		t.Errorf("B should be 3.98, but got %v", b)
+	}
+
+	// Expect the initial guess for C to be the mean value of the xData:
+	if c != 30000 {
+		t.Errorf("C should be 30000, but got %v", c)
+	}
+
+	// Expect the initial guess for D to be 0:
+	if d != 0 {
+		t.Errorf("D should be 0, but got %v", d)
+	}
+}