# Tech Tips

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Contents

# Outline

We can draw charts with Go lang using Plotinum.
I’ll draw a chart with the library.

# Install

It’s easy. Just type following command.
```go get code.google.com/p/plotinum/...
```

# Sample Program

We can check sample source codes here.
I’ll try to draw a chart represents following formula.
w is white Gaussian noise with N(1, 0.05) (average is 1 and variance is 0.05).
```package main

import (
"image/color"
"math/rand"
"math"
)

// Generate Gaussian white noise by Box-Mullar Transform
func normalRand(mu, sigma float64) float64 {
z := math.Sqrt(-2.0 * math.Log(rand.Float64())) * math.Sin(2.0 * math.Pi * rand.Float64())
return sigma*z + mu
}

// Make sequence of numbers with common difference
func linspace(start, end float64, n int, x plotter.XYs) {
for i := 0; i &amp;amp;lt; n; i++ {
t := float64(i) / float64(n-1)
x[i].X = (1.0 - t) * start + t * end
}
}

func main() {
//===================================================
// Make observed points

rand.Seed(int64(0))

// Prepare X axis of observed points
n := 50

// make observed points
pix := make([]float64, n)
for i := 0; i &amp;amp;lt; n; i++ {
}
for i := 0; i &amp;amp;lt; n; i++ {
answer[i].Y = math.Sin(pix[i]) / pix[i] + 0.1 * answer[i].X + normalRand(1.0, 0.05)
}

//====================================================
// Graph Setting

// Create a new plot, set its title and axis labels
p, err := plot.New()
if err != nil {
panic(err)
}
p.Title.Text = "Plotinum Sample"
p.X.Label.Text = "X"
p.Y.Label.Text = "Y"

// Make a scatter plotter and set its style
// Make a line plotter with points and set its style.
if err != nil {
panic(err)
}
lpLine.Color = color.RGBA{G: 255, A: 255}
lpPoints.Shape = plot.PyramidGlyph{}
lpPoints.Color = color.RGBA{R: 255, A: 255}

// Save the plot to a PNG file.
if err := p.Save(4, 4, "sample.png"); err != nil {
panic(err)
}
}
```