| // Copyright ©2018 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 distuv |
| |
| import ( |
| "math" |
| "sort" |
| "testing" |
| |
| "golang.org/x/exp/rand" |
| |
| "gonum.org/v1/gonum/floats/scalar" |
| ) |
| |
| func TestInverseGamma(t *testing.T) { |
| t.Parallel() |
| // Values extracted from a comparison with scipy |
| for _, test := range []struct { |
| x, alpha, want float64 |
| }{ |
| {0.9, 4.5, 0.050521067785046482}, |
| {0.04, 45, 0.10550644842525572}, |
| {20, 0.4, 0.0064691988681571536}, |
| } { |
| pdf := InverseGamma{Alpha: test.alpha, Beta: 1}.Prob(test.x) |
| if !scalar.EqualWithinAbsOrRel(pdf, test.want, 1e-10, 1e-10) { |
| t.Errorf("Pdf mismatch. Got %v, want %v", pdf, test.want) |
| } |
| } |
| src := rand.NewSource(1) |
| for i, g := range []InverseGamma{ |
| {Alpha: 5.6, Beta: 0.5, Src: src}, |
| {Alpha: 30, Beta: 1.7, Src: src}, |
| {Alpha: 30.2, Beta: 1.7, Src: src}, |
| } { |
| testInverseGamma(t, g, i) |
| } |
| } |
| |
| func testInverseGamma(t *testing.T, f InverseGamma, i int) { |
| const ( |
| tol = 1e-2 |
| n = 2e6 |
| bins = 50 |
| ) |
| x := make([]float64, n) |
| generateSamples(x, f) |
| sort.Float64s(x) |
| |
| testRandLogProbContinuous(t, i, 0, x, f, tol, bins) |
| checkMean(t, i, x, f, tol) |
| checkVarAndStd(t, i, x, f, 2e-2) |
| checkExKurtosis(t, i, x, f, 2e-1) |
| checkProbContinuous(t, i, x, 0, math.Inf(1), f, 1e-10) |
| checkQuantileCDFSurvival(t, i, x, f, 5e-2) |
| checkMode(t, i, x, f, 1e-2, 1e-2) |
| |
| cdf0 := f.CDF(0) |
| if cdf0 != 0 { |
| t.Errorf("Expected zero CDF at 0, but got: %v", cdf0) |
| } |
| cdfNeg := f.CDF(-0.0001) |
| if cdfNeg != 0 { |
| t.Errorf("Expected zero CDF for a negative argument, but got: %v", cdfNeg) |
| } |
| surv0 := f.Survival(0) |
| if surv0 != 1 { |
| t.Errorf("Mismatch in Survival at 0. Got %v, want 1", surv0) |
| } |
| survNeg := f.Survival(-0.0001) |
| if survNeg != 1 { |
| t.Errorf("Mismatch in Survival for a negative argument. Got %v, want 1", survNeg) |
| } |
| if f.NumParameters() != 2 { |
| t.Errorf("Mismatch in NumParameters. Got %v, want 2", f.NumParameters()) |
| } |
| pdf0 := f.Prob(0) |
| if pdf0 != 0 { |
| t.Errorf("Expected zero PDF at 0, but got: %v", pdf0) |
| } |
| pdfNeg := f.Prob(-0.0001) |
| if pdfNeg != 0 { |
| t.Errorf("Expected zero PDF for a negative argument, but got: %v", pdfNeg) |
| } |
| } |
| |
| func TestInverseGammaLowAlpha(t *testing.T) { |
| t.Parallel() |
| f := InverseGamma{Alpha: 1, Beta: 1} |
| mean := f.Mean() |
| if !math.IsInf(mean, 1) { |
| t.Errorf("Expected +Inf mean for alpha <= 1, got %v", mean) |
| } |
| f = InverseGamma{Alpha: 2, Beta: 1} |
| stdDev := f.StdDev() |
| if !math.IsInf(stdDev, 1) { |
| t.Errorf("Expected +Inf standard deviation for alpha <= 2, got %v", stdDev) |
| } |
| variance := f.Variance() |
| if !math.IsInf(variance, 1) { |
| t.Errorf("Expected +Inf variance for alpha <= 2, got %v", variance) |
| } |
| f = InverseGamma{Alpha: 4, Beta: 1} |
| exKurt := f.ExKurtosis() |
| if !math.IsInf(exKurt, 1) { |
| t.Errorf("Expected +Inf excess kurtosis for alpha <= 4, got %v", exKurt) |
| } |
| } |