github.com/gopherd/gonum@v0.0.4/stat/distmat/unit_vector_example_test.go (about)

     1  // Copyright ©2020 The Gonum Authors. All rights reserved.
     2  // Use of this source code is governed by a BSD-style
     3  // license that can be found in the LICENSE file.
     4  
     5  package distmat_test
     6  
     7  import (
     8  	"fmt"
     9  
    10  	"math/rand"
    11  
    12  	"github.com/gopherd/gonum/mat"
    13  	"github.com/gopherd/gonum/stat/distmat"
    14  )
    15  
    16  // ExampleUnitVector uses the UnitVector distribution to take
    17  // a random walk in n-space. At the end it computes how far
    18  // from the origin the walk finished.
    19  func ExampleUnitVector() {
    20  	src := rand.NewSource(1)
    21  	rnd := rand.New(src)
    22  	dist := distmat.NewUnitVector(src)
    23  
    24  	// Draw a random dimension for the space to walk through.
    25  	nDim := 1 + rnd.Intn(100)
    26  	// Vectors to hold the current position and next step.
    27  	position := mat.NewVecDense(nDim, nil)
    28  	step := mat.NewVecDense(nDim, nil)
    29  
    30  	// Draw a random number of steps to take.
    31  	nSteps := 1 + rnd.Intn(100)
    32  	for i := 0; i < nSteps; i++ {
    33  		// Draw a random step and update the position.
    34  		dist.UnitVecTo(step)
    35  		position.AddVec(position, step)
    36  	}
    37  
    38  	// Finally compute distance from the origin.
    39  	distance := mat.Norm(position, 2)
    40  	fmt.Printf("took %d steps in %d-space, walked %1.1f in total", nSteps, nDim, distance)
    41  	// Output:
    42  	// took 22 steps in 52-space, walked 5.3 in total
    43  }