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// Copyright ©2015 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 quad_test
import (
"fmt"
"math"
"runtime"
"gonum.org/v1/gonum/integrate/quad"
"gonum.org/v1/gonum/stat/distuv"
)
func Example() {
fmt.Println("Evaluate the expected value of x^2 + 3 under a Weibull distribution")
f := func(x float64) float64 {
d := distuv.Weibull{Lambda: 1, K: 1.5}
return (x*x + 3) * d.Prob(x)
}
ev := quad.Fixed(f, 0, math.Inf(1), 10, nil, 0)
fmt.Printf("EV with 10 points = %0.6v\n", ev)
ev = quad.Fixed(f, 0, math.Inf(1), 30, nil, 0)
fmt.Printf("EV with 30 points = %0.6v\n", ev)
ev = quad.Fixed(f, 0, math.Inf(1), 100, nil, 0)
fmt.Printf("EV with 100 points = %0.6v\n", ev)
ev = quad.Fixed(f, 0, math.Inf(1), 10000, nil, 0)
fmt.Printf("EV with 10000 points = %0.6v\n\n", ev)
fmt.Println("Estimate using parallel evaluations of f.")
concurrent := runtime.GOMAXPROCS(0)
ev = quad.Fixed(f, 0, math.Inf(1), 100, nil, concurrent)
fmt.Printf("EV = %0.6v\n", ev)
// Output:
// Evaluate the expected value of x^2 + 3 under a Weibull distribution
// EV with 10 points = 4.20175
// EV with 30 points = 4.19066
// EV with 100 points = 4.19064
// EV with 10000 points = 4.19064
//
// Estimate using parallel evaluations of f.
// EV = 4.19064
}
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