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// Copyright ©2020 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 interp_test
import (
"fmt"
"math"
"os"
"text/tabwriter"
"gonum.org/v1/gonum/interp"
)
func ExamplePredictor() {
// An example of fitting different interpolation
// algorithms to (X, Y) data with widely varying slope.
//
// Cubic interpolators have to balance the smoothness
// of the generated curve with suppressing ugly wiggles
// (compare the output of AkimaSpline with that of
// FritschButland).
xs := []float64{0, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11}
ys := []float64{0, 0.001, 0.002, 0.1, 1, 2, 2.5, -10, -10.01, 2.49, 2.53, 2.55}
var pc interp.PiecewiseConstant
var pl interp.PiecewiseLinear
var as interp.AkimaSpline
var fb interp.FritschButland
predictors := []interp.FittablePredictor{&pc, &pl, &as, &fb}
for i, p := range predictors {
err := p.Fit(xs, ys)
if err != nil {
panic(fmt.Sprintf("Error fitting %d-th predictor: %v", i, err))
}
}
n := len(xs)
dx := 0.25
nPts := int(math.Round(float64(n-1)/dx)) + 1
w := tabwriter.NewWriter(os.Stdout, 8, 0, 1, ' ', tabwriter.AlignRight)
fmt.Fprintln(w, "x\tPC\tPL\tAS\tFB\t")
for i := 0; i < nPts; i++ {
x := xs[0] + float64(i)*dx
fmt.Fprintf(w, "%.2f", x)
for _, predictor := range predictors {
y := predictor.Predict(x)
fmt.Fprintf(w, "\t%.2f", y)
}
fmt.Fprintln(w, "\t")
}
fmt.Fprintln(w)
w.Flush()
// Output:
// x PC PL AS FB
// 0.00 0.00 0.00 0.00 0.00
// 0.25 0.00 0.00 0.00 0.00
// 0.50 0.00 0.00 0.00 0.00
// 0.75 0.00 0.00 0.00 0.00
// 1.00 0.00 0.00 0.00 0.00
// 1.25 0.00 0.00 0.00 0.00
// 1.50 0.00 0.00 0.00 0.00
// 1.75 0.00 0.00 0.00 0.00
// 2.00 0.00 0.00 0.00 0.00
// 2.25 0.10 0.03 -0.01 0.01
// 2.50 0.10 0.05 -0.01 0.03
// 2.75 0.10 0.08 0.02 0.06
// 3.00 0.10 0.10 0.10 0.10
// 3.25 1.00 0.33 0.26 0.22
// 3.50 1.00 0.55 0.49 0.45
// 3.75 1.00 0.78 0.75 0.73
// 4.00 1.00 1.00 1.00 1.00
// 4.25 2.00 1.25 1.24 1.26
// 4.50 2.00 1.50 1.50 1.54
// 4.75 2.00 1.75 1.75 1.79
// 5.00 2.00 2.00 2.00 2.00
// 5.25 2.50 2.12 2.22 2.17
// 5.50 2.50 2.25 2.37 2.33
// 5.75 2.50 2.38 2.47 2.45
// 6.00 2.50 2.50 2.50 2.50
// 6.25 -10.00 -0.62 0.83 0.55
// 6.50 -10.00 -3.75 -2.98 -3.75
// 6.75 -10.00 -6.88 -7.18 -8.04
// 7.00 -10.00 -10.00 -10.00 -10.00
// 7.25 -10.01 -10.00 -11.16 -10.00
// 7.50 -10.01 -10.00 -11.55 -10.01
// 7.75 -10.01 -10.01 -11.18 -10.01
// 8.00 -10.01 -10.01 -10.01 -10.01
// 8.25 2.49 -6.88 -7.18 -8.06
// 8.50 2.49 -3.76 -2.99 -3.77
// 8.75 2.49 -0.63 0.82 0.53
// 9.00 2.49 2.49 2.49 2.49
// 9.25 2.53 2.50 2.50 2.51
// 9.50 2.53 2.51 2.51 2.52
// 9.75 2.53 2.52 2.52 2.52
// 10.00 2.53 2.53 2.53 2.53
// 10.25 2.55 2.53 2.54 2.54
// 10.50 2.55 2.54 2.54 2.54
// 10.75 2.55 2.54 2.55 2.55
// 11.00 2.55 2.55 2.55 2.55
}
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