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

     1  // Copyright ©2016 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 stat_test
     6  
     7  import (
     8  	"fmt"
     9  
    10  	"github.com/gopherd/gonum/mat"
    11  	"github.com/gopherd/gonum/stat"
    12  )
    13  
    14  func ExamplePC() {
    15  	// iris is a truncated sample of the Fisher's Iris dataset.
    16  	n := 10
    17  	d := 4
    18  	iris := mat.NewDense(n, d, []float64{
    19  		5.1, 3.5, 1.4, 0.2,
    20  		4.9, 3.0, 1.4, 0.2,
    21  		4.7, 3.2, 1.3, 0.2,
    22  		4.6, 3.1, 1.5, 0.2,
    23  		5.0, 3.6, 1.4, 0.2,
    24  		5.4, 3.9, 1.7, 0.4,
    25  		4.6, 3.4, 1.4, 0.3,
    26  		5.0, 3.4, 1.5, 0.2,
    27  		4.4, 2.9, 1.4, 0.2,
    28  		4.9, 3.1, 1.5, 0.1,
    29  	})
    30  
    31  	// Calculate the principal component direction vectors
    32  	// and variances.
    33  	var pc stat.PC
    34  	ok := pc.PrincipalComponents(iris, nil)
    35  	if !ok {
    36  		return
    37  	}
    38  	fmt.Printf("variances = %.4f\n\n", pc.VarsTo(nil))
    39  
    40  	// Project the data onto the first 2 principal components.
    41  	k := 2
    42  	var proj mat.Dense
    43  	var vec mat.Dense
    44  	pc.VectorsTo(&vec)
    45  	proj.Mul(iris, vec.Slice(0, d, 0, k))
    46  
    47  	fmt.Printf("proj = %.4f", mat.Formatted(&proj, mat.Prefix("       ")))
    48  
    49  	// Output:
    50  	// variances = [0.1666 0.0207 0.0079 0.0019]
    51  	//
    52  	// proj = ⎡-6.1686   1.4659⎤
    53  	//        ⎢-5.6767   1.6459⎥
    54  	//        ⎢-5.6699   1.3642⎥
    55  	//        ⎢-5.5643   1.3816⎥
    56  	//        ⎢-6.1734   1.3309⎥
    57  	//        ⎢-6.7278   1.4021⎥
    58  	//        ⎢-5.7743   1.1498⎥
    59  	//        ⎢-6.0466   1.4714⎥
    60  	//        ⎢-5.2709   1.3570⎥
    61  	//        ⎣-5.7533   1.6207⎦
    62  }