Overview
Usually when I plot data’s behavior to check it and to decide the approach, I use Python, matplotlib. Actually these days this is one of the best answer from the viewpoint of data science. But for these 3 or 4 weeks, I have been using Go and as a data scientist, I feel obligation to know how to plot data even at a basic level.This is basic plot note about Golang.
Environment
Data
This time, I just used normal random number.
Library
gonum/plot has typical plot functions. You can install by “go get”. If the error about hg appear, you can install mercurial by brew(if you are Mac user.).
Make Simple graphs
Code
The code below has three types of simple plots. Box plot, Bar plot, Histogram.
Those plots have no decoration even about the aspect of color.
package main
import (
"github.com/gonum/plot"
"github.com/gonum/plot/plotter"
"github.com/gonum/plot/vg"
"math/rand"
)
func main() {
//make data
var values plotter.Values
for i := 0; i < 1000; i++ {
values = append(values, rand.NormFloat64())
}
boxPlot(values)
barPlot(values[:4])
histPlot(values)
}
func boxPlot(values plotter.Values) {
p, err := plot.New()
if err != nil {
panic(err)
}
p.Title.Text = "box plot"
box, err := plotter.NewBoxPlot(vg.Length(15), 0.0, values)
if err != nil {
panic(err)
}
p.Add(box)
if err := p.Save(3*vg.Inch, 3*vg.Inch, "box.png"); err != nil {
panic(err)
}
}
func barPlot(values plotter.Values) {
p, err := plot.New()
if err != nil {
panic(err)
}
p.Title.Text = "bar plot"
bar, err := plotter.NewBarChart(values, 15)
if err != nil {
panic(err)
}
p.Add(bar)
if err := p.Save(3*vg.Inch, 3*vg.Inch, "bar.png"); err != nil {
panic(err)
}
}
func histPlot(values plotter.Values) {
p, err := plot.New()
if err != nil {
panic(err)
}
p.Title.Text = "histogram plot"
hist, err := plotter.NewHist(values, 20)
if err != nil {
panic(err)
}
p.Add(hist)
if err := p.Save(3*vg.Inch, 3*vg.Inch, "hist.png"); err != nil {
panic(err)
}
}When you execute this code, three simple plot images are saved.
Let’s check one by one.
Box plot
Box plot is the plot which contains qunantile points information and outliers. You can check the distributions of the given values.
func boxPlot(values plotter.Values) {
p, err := plot.New()
if err != nil {
panic(err)
}
p.Title.Text = "box plot"
box, err := plotter.NewBoxPlot(vg.Length(15), 0.0, values)
if err != nil {
panic(err)
}
p.Add(box)
if err := p.Save(3*vg.Inch, 3*vg.Inch, "box.png"); err != nil {
panic(err)
}
}The plot saved by this is this image.
Bar plot
Actually, I don’t use bar plot much. But sometimes, to emphasize, it works well.
func barPlot(values plotter.Values) {
p, err := plot.New()
if err != nil {
panic(err)
}
p.Title.Text = "bar plot"
bar, err := plotter.NewBarChart(values, 15)
if err != nil {
panic(err)
}
p.Add(bar)
if err := p.Save(3*vg.Inch, 3*vg.Inch, "bar.png"); err != nil {
panic(err)
}
}This is also simple as box plot. The function plotter.NewBarChart() takes two arguments. First one is target data and the second is part’s width.
The plot image is like this.
Histogram
Histogram is one of the fundamental tool for data analysis.
func histPlot(values plotter.Values) {
p, err := plot.New()
if err != nil {
panic(err)
}
p.Title.Text = "histogram plot"
hist, err := plotter.NewHist(values, 20)
if err != nil {
panic(err)
}
p.Add(hist)
if err := p.Save(3*vg.Inch, 3*vg.Inch, "hist.png"); err != nil {
panic(err)
}
}About histogram, there is a point. plotter.NewHist() takes 2 arguments and the second one means bins number. By the number of bins, the histogram looks different and it sometimes leads to misjudges to data.
Make graph fancy
I made three types simple graphs. Those are too simple. Even if I’m not visualizing-oriented, I don’t like those as those are. I try to make it look better, focusing on histogram.
Histogram structure can take Bins, Width, FillColor, draw.LineStyle. So, I’ll add FillColor and draw.LineStyle.
At first, just colors.
func histPlot(values plotter.Values) {
p, err := plot.New()
if err != nil {
panic(err)
}
p.Title.Text = "histogram plot"
hist, err := plotter.NewHist(values, 20)
if err != nil {
panic(err)
}
hist.FillColor = plotutil.Color(2)
p.Add(hist)
if err := p.Save(3*vg.Inch, 3*vg.Inch, "hist.png"); err != nil {
panic(err)
}
}
By setting plotutil.Color() to FillColor, the graph can get color. Easily, you can change color by changing the value of the argument.
Next, LineStyle.
func histPlot(values plotter.Values) {
p, err := plot.New()
if err != nil {
panic(err)
}
p.Title.Text = "histogram plot"
hist, err := plotter.NewHist(values, 20)
if err != nil {
panic(err)
}
hist.FillColor = plotutil.Color(2)
hist.LineStyle.Color = plotutil.Color(4)
p.Add(hist)
if err := p.Save(3*vg.Inch, 3*vg.Inch, "hist_cl.png"); err != nil {
panic(err)
}
}The structure LineStyle has Color, Width, Dashes, DashOffs. On this code, I just set Color. The image is like this. Line parts have red.
