# Golang : Create matrix with Gonum Matrix package example

Here is an example of how to create and display matrix properly in Golang with Gonum package. Nothing special in this tutorial, will write another tutorial on how to find the matrix determinants and performing matrix calculations later on.

Here you go!

`````` package main

import (
"fmt"
"github.com/gonum/matrix/mat64"
)

func main() {
m := mat64.NewDense(3, 5, nil)

// fill in m with some elements
for i := 0; i < 3; i++ {
m.Set(i, i, 99)
}

// wrong way to print matrix
fmt.Println("m : ", m)

// proper way
// refer to https://godoc.org/github.com/gonum/matrix/mat64#Excerpt
fmt.Printf("m :\n%v\n\n", mat64.Formatted(m, mat64.Prefix(" "), mat64.Excerpt(2)))

// print all m elements
fmt.Printf("m :\n%v\n\n", mat64.Formatted(m, mat64.Prefix(""), mat64.Excerpt(0)))

data := []float64{1, 2, 3}
m2 := mat64.NewDense(3, 1, data)

// print all m2 elements
fmt.Printf("m2 :\n%v\n\n", mat64.Formatted(m2, mat64.Prefix(""), mat64.Excerpt(0)))

// to build this matrix
// ⎡1  2  3⎤
// ⎢4  5  6⎥
// ⎣7  8  9⎦

// use SetRow or SetCol
m3 := mat64.NewDense(3, 3, nil)
m3.SetRow(0, data)

data2 := []float64{4, 5, 6}
m3.SetRow(1, data2)

data3 := []float64{7, 8, 9}
m3.SetRow(2, data3)

// print all m3 elements
fmt.Printf("m3 :\n%v\n\n", mat64.Formatted(m3, mat64.Prefix(""), mat64.Excerpt(0)))

// get transpose with m3.T()
fmt.Printf("m3 transpose :\n%v\n\n", mat64.Formatted(m3.T(), mat64.Prefix(""), mat64.Excerpt(0)))

}
``````

Output:

m : &{{3 5 5 [99 0 0 0 0 0 99 0 0 0 0 0 99 0 0]} 3 5}

m :

Dims(3, 5)

⎡99 0 ... ... 0 0⎤

⎢ 0 99 0 0⎥

⎣ 0 0 ... ... 0 0⎦

m :

⎡99 0 0 0 0⎤

⎢ 0 99 0 0 0⎥

⎣ 0 0 99 0 0⎦

m2 :

⎡1⎤

⎢2⎥

⎣3⎦

m3 :

⎡1 2 3⎤

⎢4 5 6⎥

⎣7 8 9⎦

m3 transpose :

⎡1 4 7⎤

⎢2 5 8⎥

⎣3 6 9⎦

References:

https://godoc.org/github.com/gonum/matrix/mat64#Dense.SetRow

https://github.com/gonum/matrix