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LeastSquaresMethod.go
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/
LeastSquaresMethod.go
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package main
import (
"fmt"
"gonum.org/v1/plot"
"gonum.org/v1/plot/plotter"
"gonum.org/v1/plot/vg"
"log"
"os"
)
type xy struct {
x []float64
y []float64
}
func (d xy) Len() int {
return len(d.x)
}
func (d xy) XY(i int) (x, y float64) {
x = d.x[i]
y = d.y[i]
return
}
type Point struct {
x float64
y float64
}
func LeastSquaresMethod(points *[]Point) (a float64, b float64) {
n := float64(len(*points))
sumX := 0.0
sumY := 0.0
sumXY := 0.0
sumXX := 0.0
for _, p := range *points {
sumX += p.x
sumY += p.y
sumXY += p.x * p.y
sumXX += p.x * p.x
}
base := n*sumXX - sumX*sumX
a = (n*sumXY - sumX*sumY) / base
b = (sumXX*sumY - sumXY*sumX) / base
return a, b
}
//func Rotate(p Point, alpha float64) Point {
// newPoint := Point{
// x: p.x*math.Cos(alpha) - p.y*math.Sin(alpha),
// y: p.x*math.Sin(alpha) + p.y*math.Cos(alpha),
// }
// return newPoint
//}
func Plot(a float64, b float64, points *[]Point, numberOfPoint int) {
data := xy{
x: make([]float64, numberOfPoint),
y: make([]float64, numberOfPoint),
}
var i int
i = 0
for _, p := range *points {
data.x[i] = p.x
data.y[i] = p.y
i += 1
}
log.Printf("%v*x+%v", a, b)
line := plotter.NewFunction(func(x float64) float64 { return a*x + b })
p := plot.New()
plotter.DefaultLineStyle.Width = vg.Points(1)
plotter.DefaultGlyphStyle.Radius = vg.Points(2)
scatter, err := plotter.NewScatter(data)
if err != nil {
log.Panic(err)
}
p.Add(scatter, line)
w, err := p.WriterTo(300, 300, "svg")
if err != nil {
log.Panic(err)
}
_, err = w.WriteTo(os.Stdout)
if err != nil {
log.Panic(err)
}
}
func main() {
points := make([]Point, 0)
var numberOfPoints int
//alpha := math.Pi / 2
file, err := os.Open("points.txt")
if err != nil {
fmt.Println(err)
}
_, _ = fmt.Fscan(file, &numberOfPoints)
for i := 0; i < numberOfPoints; i++ {
var currentPoint Point
_, _ = fmt.Fscan(file, ¤tPoint.x)
_, _ = fmt.Fscan(file, ¤tPoint.y)
log.Print(currentPoint, " ")
points = append(points, currentPoint)
}
log.Print("\n")
a, b := LeastSquaresMethod(&points)
log.Print("Before rotation", "\n")
log.Println("a= ", a)
log.Println("b= ", b)
Plot(a, b, &points, numberOfPoints)
//for i := 0; i < numberOfPoints; i++ {
// points[i] = Rotate(points[i], alpha)
//}
//
//a, b = LeastSquaresMethod(&points)
//log.Print("After rotation", "\n")
//log.Println("a= ", a)
//log.Println("b= ", b)
//
//Plot(a, b, &points, numberOfPoints)
}