go wrapper for chartjs
Chartjs charts are defined purely in JSON, so this library is mostly structs and struct-tags that dictate how to marshal to JSON. None of the currently implemented parts are stringly-typed in this library so it can avoid many errors.
The chartjs javascript/JSON api has a lot of surface area. Currently, only the options that I use are provided. More can and will be added as I need them (or via pull-requests).
There is a small amount of code to simplify creating charts.
data to be plotted by chartjs has to meet this interface.
type Values interface {
// X-axis values. If only these are specified then it must be a Bar plot.
Xs() []float64
// Optional Y values.
Ys() []float64
// Rs are used to size points for chartType `Bubble`. If this returns an
// empty slice then it's not used.
Rs() []float64
}This longish example shows common use of the library.
package main
import (
"log"
"math"
"os"
chartjs "github.com/brentp/go-chartjs"
)
// satisfy the required interface with this struct and methods.
type xy struct {
x []float64
y []float64
r []float64
}
func (v xy) Xs() []float64 {
return v.x
}
func (v xy) Ys() []float64 {
return v.y
}
func (v xy) Rs() []float64 {
return v.r
}
func check(e error) {
if e != nil {
log.Fatal(e)
}
}
func main() {
var xys1 xy
var xys2 xy
// make some example data.
for i := float64(0); i < 9; i += 0.1 {
xys1.x = append(xys1.x, i)
xys2.x = append(xys2.x, i)
xys1.y = append(xys1.y, math.Sin(i))
xys2.y = append(xys2.y, 3*math.Cos(2*i))
}
// a set of colors to work with.
colors := []*types.RGBA{
&types.RGBA{102, 194, 165, 220},
&types.RGBA{250, 141, 98, 220},
&types.RGBA{141, 159, 202, 220},
&types.RGBA{230, 138, 195, 220},
}
// a Dataset contains the data and styling info.
d1 := chartjs.Dataset{Data: xys1, BorderColor: colors[1], Label: "sin(x)", Fill: chartjs.False,
PointRadius: 10, PointBorderWidth: 4, BackgroundColor: colors[0]}
d2 := chartjs.Dataset{Data: xys2, BorderWidth: 8, BorderColor: colors[3], Label: "3*cos(2*x)",
Fill: chartjs.False, PointStyle: chartjs.Star}
chart := chartjs.Chart{Label: "test-chart"}
var err error
_, err = chart.AddXAxis(chartjs.Axis{Type: chartjs.Linear, Position: chartjs.Bottom, ScaleLabel: &chartjs.ScaleLabel{FontSize: 22, LabelString: "X", Display: chartjs.True}})
check(err)
d1.YAxisID, err = chart.AddYAxis(chartjs.Axis{Type: chartjs.Linear, Position: chartjs.Left,
ScaleLabel: &chartjs.ScaleLabel{LabelString: "sin(x)", Display: chartjs.True}})
check(err)
chart.AddDataset(d1)
d2.YAxisID, err = chart.AddYAxis(chartjs.Axis{Type: chartjs.Linear, Position: chartjs.Right,
ScaleLabel: &chartjs.ScaleLabel{LabelString: "3*cos(2*x)", Display: chartjs.True}})
check(err)
chart.AddDataset(d2)
chart.Options.Responsive = chartjs.False
wtr, err := os.Create("example-chartjs-multi.html")
if err != nil {
}
if err := chart.SaveHTML(wtr, nil); err != nil {
log.Fatal(err)
}
wtr.Close()
}The resulting html will have an interactive <canvas> element that looks like this.
