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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 }