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trapezoidal_test.go
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/
trapezoidal_test.go
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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 integrate
import (
"math"
"testing"
"github.com/gonum/floats"
)
func TestTrapezoidal(t *testing.T) {
const N = 1e6
x := floats.Span(make([]float64, N), 0, 1)
for i, test := range []struct {
x []float64
f func(x float64) float64
want float64
}{
{
x: x,
f: func(x float64) float64 { return x },
want: 0.5,
},
{
x: floats.Span(make([]float64, N), -1, 1),
f: func(x float64) float64 { return x },
want: 0,
},
{
x: x,
f: func(x float64) float64 { return x + 10 },
want: 10.5,
},
{
x: x,
f: func(x float64) float64 { return 3*x*x + 10 },
want: 11,
},
{
x: x,
f: func(x float64) float64 { return math.Exp(x) },
want: 1.7182818284591876,
},
{
x: floats.Span(make([]float64, N), 0, math.Pi),
f: func(x float64) float64 { return math.Cos(x) },
want: 0,
},
{
x: floats.Span(make([]float64, N), 0, 2*math.Pi),
f: func(x float64) float64 { return math.Cos(x) },
want: 0,
},
{
x: floats.Span(make([]float64, N*10), 0, math.Pi),
f: func(x float64) float64 { return math.Sin(x) },
want: 2,
},
{
x: floats.Span(make([]float64, N*10), 0, 0.5*math.Pi),
f: func(x float64) float64 { return math.Sin(x) },
want: 1,
},
{
x: floats.Span(make([]float64, N), 0, 2*math.Pi),
f: func(x float64) float64 { return math.Sin(x) },
want: 0,
},
} {
y := make([]float64, len(test.x))
for i, v := range test.x {
y[i] = test.f(v)
}
v := Trapezoidal(test.x, y)
if !floats.EqualWithinAbs(v, test.want, 1e-12) {
t.Errorf("test #%d: got=%v want=%v\n", i, v, test.want)
}
}
}