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// Copyright ©2016 The Gonum Authors. All rights reserved.
// Use of this source code is governed by a BSD-style
// license that can be found in the LICENSE file.
package stat_test
import (
"fmt"
"gonum.org/v1/gonum/mat"
"gonum.org/v1/gonum/stat"
)
func ExamplePC() {
// iris is a truncated sample of the Fisher's Iris dataset.
n := 10
d := 4
iris := mat.NewDense(n, d, []float64{
5.1, 3.5, 1.4, 0.2,
4.9, 3.0, 1.4, 0.2,
4.7, 3.2, 1.3, 0.2,
4.6, 3.1, 1.5, 0.2,
5.0, 3.6, 1.4, 0.2,
5.4, 3.9, 1.7, 0.4,
4.6, 3.4, 1.4, 0.3,
5.0, 3.4, 1.5, 0.2,
4.4, 2.9, 1.4, 0.2,
4.9, 3.1, 1.5, 0.1,
})
// Calculate the principal component direction vectors
// and variances.
var pc stat.PC
ok := pc.PrincipalComponents(iris, nil)
if !ok {
return
}
fmt.Printf("variances = %.4f\n\n", pc.VarsTo(nil))
// Project the data onto the first 2 principal components.
k := 2
var proj mat.Dense
var vec mat.Dense
pc.VectorsTo(&vec)
proj.Mul(iris, vec.Slice(0, d, 0, k))
fmt.Printf("proj = %.4f", mat.Formatted(&proj, mat.Prefix(" ")))
// Output:
// variances = [0.1666 0.0207 0.0079 0.0019]
//
// proj = ⎡-6.1686 1.4659⎤
// ⎢-5.6767 1.6459⎥
// ⎢-5.6699 1.3642⎥
// ⎢-5.5643 1.3816⎥
// ⎢-6.1734 1.3309⎥
// ⎢-6.7278 1.4021⎥
// ⎢-5.7743 1.1498⎥
// ⎢-6.0466 1.4714⎥
// ⎢-5.2709 1.3570⎥
// ⎣-5.7533 1.6207⎦
}
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