Simple linear regression with plot in go with gonum

README.md

Very simple linear regression

curl -s //www.lauradhamilton.com/data_files/cricket_chirps_versus_temperature.txt | go run main.go > output.svg
2018/06/13 19:57:59 3.3057614388773593*x+24.966014428303183

main.go

package main

import (
        "encoding/csv"
        "log"
        "os"
        "strconv"

        "gonum.org/v1/gonum/stat"
        "gonum.org/v1/plot"
        "gonum.org/v1/plot/plotter"
        "gonum.org/v1/plot/vg"
)

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
}
func main() {
        r := csv.NewReader(os.Stdin)

        records, err := r.ReadAll()
        if err != nil {
                log.Fatal(err)
        }
        size := len(records)
        data := xy{
                x: make([]float64, size),
                y: make([]float64, size),
        }
        for i, v := range records {
                if len(v) != 2 {
                        log.Fatal("Expected two elements")
                }
                if s, err := strconv.ParseFloat(v[0], 64); err == nil {
                                          data.y[i] = s
                }
                if s, err := strconv.ParseFloat(v[1], 64); err == nil {
                        data.x[i] = s
                }
        }
        b, a := stat.LinearRegression(data.x, data.y, nil, false)
        log.Printf("%v*x+%v", a, b)
        line := plotter.NewFunction(func(x float64) float64 { return a*x + b })

        p, err := plot.New()
        if err != nil {
                log.Panic(err)
        }

        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)
        }
}

result.svg

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