gonum.org/v1/gonum@v0.14.0/mat/qr_example_test.go (about)

     1  // Copyright ©2022 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  	"gonum.org/v1/gonum/mat"
    12  )
    13  
    14  func ExampleQR_solveTo() {
    15  	// QR factorization can be used for solving linear inverse problems,
    16  	// as this is a more numerically stable technique than direct
    17  	// matrix inversion.
    18  	//
    19  	// Here, we want to solve:
    20  	//   Ax = b
    21  
    22  	var (
    23  		a = mat.NewDense(4, 2, []float64{0, 1, 1, 1, 1, 1, 2, 1})
    24  		b = mat.NewDense(4, 1, []float64{1, 0, 2, 1})
    25  		x = mat.NewDense(2, 1, nil)
    26  	)
    27  
    28  	var qr mat.QR
    29  	qr.Factorize(a)
    30  
    31  	err := qr.SolveTo(x, false, b)
    32  	if err != nil {
    33  		log.Fatalf("could not solve QR: %+v", err)
    34  	}
    35  	fmt.Printf("%.3f\n", mat.Formatted(x))
    36  
    37  	// Output:
    38  	// ⎡0.000⎤
    39  	// ⎣1.000⎦
    40  }