github.com/gopherd/gonum@v0.0.4/mat/eigen_example_test.go (about)

     1  // Copyright ©2018 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 mat_test
     6  
     7  import (
     8  	"fmt"
     9  	"log"
    10  
    11  	"github.com/gopherd/gonum/mat"
    12  )
    13  
    14  func ExampleEigenSym() {
    15  	a := mat.NewSymDense(2, []float64{
    16  		7, 0.5,
    17  		0.5, 1,
    18  	})
    19  	fmt.Printf("A = %v\n\n", mat.Formatted(a, mat.Prefix("    ")))
    20  
    21  	var eigsym mat.EigenSym
    22  	ok := eigsym.Factorize(a, true)
    23  	if !ok {
    24  		log.Fatal("Symmetric eigendecomposition failed")
    25  	}
    26  	fmt.Printf("Eigenvalues of A:\n%1.3f\n\n", eigsym.Values(nil))
    27  
    28  	var ev mat.Dense
    29  	eigsym.VectorsTo(&ev)
    30  	fmt.Printf("Eigenvectors of A:\n%1.3f\n\n", mat.Formatted(&ev))
    31  
    32  	// Output:
    33  	// A = ⎡  7  0.5⎤
    34  	//     ⎣0.5    1⎦
    35  	//
    36  	// Eigenvalues of A:
    37  	// [0.959 7.041]
    38  	//
    39  	// Eigenvectors of A:
    40  	// ⎡ 0.082  -0.997⎤
    41  	// ⎣-0.997  -0.082⎦
    42  	//
    43  }
    44  
    45  func ExampleEigen() {
    46  	a := mat.NewDense(2, 2, []float64{
    47  		1, -1,
    48  		1, 1,
    49  	})
    50  	fmt.Printf("A = %v\n\n", mat.Formatted(a, mat.Prefix("    ")))
    51  
    52  	var eig mat.Eigen
    53  	ok := eig.Factorize(a, mat.EigenLeft)
    54  	if !ok {
    55  		log.Fatal("Eigendecomposition failed")
    56  	}
    57  	fmt.Printf("Eigenvalues of A:\n%v\n", eig.Values(nil))
    58  
    59  	// Output:
    60  	// A = ⎡ 1  -1⎤
    61  	//     ⎣ 1   1⎦
    62  	//
    63  	// Eigenvalues of A:
    64  	// [(1+1i) (1-1i)]
    65  }