Sparkline experiment

spark.go

package main

import (
	"github.com/ajstarks/svgo"
	"os"
)

var canvas = svg.New(os.Stdout)

// sparkline defines the components of the sparkline:
// text: label, data: data points, min/max: data range, rmin/rmax: highlighted range
type sparkline struct {
	text                 string
	data                 []float64
	min, max, rmin, rmax float64
}

// vmap maps one range to another
func vmap(value, low1, high1, low2, high2 float64) float64 {
	return low2 + (high2-low2)*(value-low1)/(high1-low1)
}

// datarange draws a datarange
func (s *sparkline) datarange(x, y, w, h int, color string) {
	if s.rmin >= s.rmax || s.rmin < s.min || s.rmax > s.max {
		return
	}
	_, dy1 := s.sparkdim(x, y, w, h, 0, s.rmax)
	_, dy2 := s.sparkdim(x, y, w, h, 0, s.rmin)
	canvas.Rect(x, y-dy1, w, dy1-dy2, "fill-opacity:0.2;fill:"+color)
}

// sparkdim returns the device coordinates
func (s *sparkline) sparkdim(x, y, w, h, i int, v float64) (int, int) {
	dx := int(vmap(float64(i), 0, float64(len(s.data)), float64(x), float64(x+w)))
	dy := int(vmap(v, s.min, s.max, 0, float64(h)))
	return dx, dy
}

// label makes the sparkline label
func (s *sparkline) label(x, y, w, h int) {
	canvas.Text(x-5, y, s.text, "text-anchor:end")
}

// bar makes a barchart
func (s *sparkline) bar(x, y, w, h int, color string) {
	s.label(x, y, w, h)
	canvas.Gstyle("stroke:" + color)
	for i, v := range s.data {
		dx, dy := s.sparkdim(x, y, w, h, i, v)
		canvas.Line(dx, y, dx, y-dy)
	}
	canvas.Gend()
	s.datarange(x, y, w, h, color)
}

// line makes a line graph
func (s *sparkline) line(x, y, w, h int, color string) {
	s.label(x, y, w, h)
	canvas.Gstyle("stroke:" + color)
	for i := 0; i < len(s.data)-1; i++ {
		dx1, dy1 := s.sparkdim(x, y, w, h, i, s.data[i])
		dx2, dy2 := s.sparkdim(x, y, w, h, i+1, s.data[i+1])
		canvas.Line(dx1, y-dy1, dx2, y-dy2)
	}
	canvas.Gend()
	s.datarange(x, y, w, h, color)
}

// area makes a area chart sparkline
func (s *sparkline) area(x, y, w, h int, color string) {
	s.label(x, y, w, h)
	xa := make([]int, len(s.data)+1)
	ya := make([]int, len(s.data)+1)
	var dx, dy int
	for i, v := range s.data {
		dx, dy = s.sparkdim(x, y, w, h, i, v)
		if i == 0 {
			xa[0] = dx
			ya[0] = y
		}
		xa[i+1] = dx
		ya[i+1] = y - dy
	}
	xa = append(xa, dx)
	ya = append(ya, y)
	canvas.Polygon(xa, ya, "fill-opacity:0.7;fill:"+color)
	s.datarange(x, y, w, h, color)
}

func main() {
	sparks := []sparkline{

		{text: "SNY",  data: []float64{47.47, 46.64, 46.70, 47.49, 47.99, 48.24, 47.83, 49.41, 49.32, 50.86, 50.36, 49.76, 49.72, 50.23, 49.77, 49.69, 50.01, 48.45, 49.57, 49.23, 48.11}, min: 45, max: 55, rmin: 48, rmax: 50},
		{text: "GOOG", data: []float64{608.42, 594.97, 594.89, 611.97, 625.80, 622.36, 622.69, 635.44, 629.25, 642.90, 635.98, 635.14, 623.24, 625.77, 621.35, 612.72, 614.66, 600.70, 606.25, 614.34, 597.79}, min: 570, max: 650, rmin: 600, rmax: 620},
		{text: "AAPL", data: []float64{109.83, 108.60, 111.96, 114.22, 114.51, 113.83, 112.92, 114.72, 112.97, 113.43, 115.91, 115.78, 114.82, 113.72, 112.09, 109.68, 111.83, 108.80, 109.90, 111.86, 107.26}, min: 100, max: 120, rmin: 110, rmax: 115},
		{text: "FAKE", data: []float64{10, 20, 30, 40, 50, 60, 70, 80, 90, 100, 110, 120, 130, 140, 150}, min: 0, max: 200, rmin: 20, rmax: 50},
	}

	width, height := 700, 700
	x, y := 100, 200
	linespacing := 75
	canvas.Start(width, height)
	canvas.Gstyle("font-family:sans-serif,Calibri;font-size:14pt")
	for _, s := range sparks {
		s.bar(x, y, 100, 50, "rgb(127,0,0)")
		s.area(x+200, y, 100, 50, "lightsteelblue")
		s.line(x+400, y, 100, 50, "black")
		y += linespacing
	}
	canvas.Gend()
	canvas.End()
}