Plotting in Go with gonum/plot.

data.txt

6.1101,17.592
5.5277,9.1302
8.5186,13.662
7.0032,11.854
5.8598,6.8233
8.3829,11.886
7.4764,4.3483
8.5781,12
6.4862,6.5987
5.0546,3.8166
5.7107,3.2522
14.164,15.505
5.734,3.1551
8.4084,7.2258
5.6407,0.71618
5.3794,3.5129
6.3654,5.3048
5.1301,0.56077
6.4296,3.6518
7.0708,5.3893
6.1891,3.1386
20.27,21.767
5.4901,4.263
6.3261,5.1875
5.5649,3.0825
18.945,22.638
12.828,13.501
10.957,7.0467
13.176,14.692
22.203,24.147
5.2524,-1.22
6.5894,5.9966
9.2482,12.134
5.8918,1.8495
8.2111,6.5426
7.9334,4.5623
8.0959,4.1164
5.6063,3.3928
12.836,10.117
6.3534,5.4974
5.4069,0.55657
6.8825,3.9115
11.708,5.3854
5.7737,2.4406
7.8247,6.7318
7.0931,1.0463
5.0702,5.1337
5.8014,1.844
11.7,8.0043
5.5416,1.0179
7.5402,6.7504
5.3077,1.8396
7.4239,4.2885
7.6031,4.9981
6.3328,1.4233
6.3589,-1.4211
6.2742,2.4756
5.6397,4.6042
9.3102,3.9624
9.4536,5.4141
8.8254,5.1694
5.1793,-0.74279
21.279,17.929
14.908,12.054
18.959,17.054
7.2182,4.8852
8.2951,5.7442
10.236,7.7754
5.4994,1.0173
20.341,20.992
10.136,6.6799
7.3345,4.0259
6.0062,1.2784
7.2259,3.3411
5.0269,-2.6807
6.5479,0.29678
7.5386,3.8845
5.0365,5.7014
10.274,6.7526
5.1077,2.0576
5.7292,0.47953
5.1884,0.20421
6.3557,0.67861
9.7687,7.5435
6.5159,5.3436
8.5172,4.2415
9.1802,6.7981
6.002,0.92695
5.5204,0.152
5.0594,2.8214
5.7077,1.8451
7.6366,4.2959
5.8707,7.2029
5.3054,1.9869
8.2934,0.14454
13.394,9.0551
5.4369,0.61705

plotwithgo.go

package main

import (
	"bufio"
	"fmt"
	"image/color"
	"log"
	"os"

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

func main() {
	xys, err := readData("data.txt")
	if err != nil {
		log.Fatalf("cound not read data.txt: %v", err)
	}

	err = plotData("out.png", xys)
	if err != nil {
		log.Fatalf("could not plot data: %v", err)
	}
}

// xy
type xy struct{ x, y float64 }

func readData(path string) (plotter.XYs, error) {
	f, err := os.Open(path)
	if err != nil {
		return nil, err
	}
	defer f.Close()

	var xys plotter.XYs
	s := bufio.NewScanner(f)
	// for every line in file...
	for s.Scan() {
		var x, y float64
		_, err := fmt.Sscanf(s.Text(), "%f,%f", &x, &y)
		if err != nil {
			log.Printf("descarding bad data point %q: %v", s.Text(), err)
		}
		// ...append the data to plotter.XYs
		xys = append(xys, struct{ X, Y float64 }{x, y})
	}
	if err := s.Err(); err != nil {
		return nil, fmt.Errorf("could not scan: %v", err)
	}
	return xys, nil
}

func plotData(path string, xys plotter.XYs) error {
	// create file to write image to
	f, err := os.Create(path)
	if err != nil {
		log.Fatalf("could not create %s: %v", path, err)
	}

	// initilize the canvas
	p, err := plot.New()
	if err != nil {
		log.Fatalf("could not create a plot: %v", err)
	}

	// create scatter with all data points
	s, err := plotter.NewScatter(xys)
	if err != nil {
		return fmt.Errorf("could not create scatter: %v", err)
	}

	// styling can be changed after scatter has been initialized
	s.GlyphStyle.Shape = draw.CrossGlyph{}
	s.Color = color.RGBA{R: 255, A: 255}
	p.Add(s) // add the scatter to the plot

	wt, err := p.WriterTo(256, 256, "png")
	if err != nil {
		log.Fatalf("could not create writer: %v", err)
	}
	f, err = os.Create("out.png")
	if err != nil {
		log.Fatalf("could not craete out.png: %v", err)
	}
	defer f.Close()
	_, err = wt.WriteTo(f)
	if err != nil {
		log.Fatalf("could not write to out.png: %v", err)
	}

	return err
}