1 // test_inverse_chi_squared.cpp
3 // Copyright Paul A. Bristow 2010.
4 // Copyright John Maddock 2010.
6 // Use, modification and distribution are subject to the
7 // Boost Software License, Version 1.0.
8 // (See accompanying file LICENSE_1_0.txt
9 // or copy at http://www.boost.org/LICENSE_1_0.txt)
12 # pragma warning (disable : 4310) // cast truncates constant value.
15 // http://www.wolframalpha.com/input/?i=inverse+chisquare+distribution
17 #include <boost/math/concepts/real_concept.hpp> // for real_concept
18 using ::boost::math::concepts::real_concept;
20 //#include <boost/math/tools/test.hpp>
21 #include <boost/test/test_exec_monitor.hpp> // for test_main
22 #include <boost/test/floating_point_comparison.hpp> // for BOOST_CHECK_CLOSE_FRACTION
24 #include <boost/math/distributions/inverse_chi_squared.hpp> // for inverse_chisquared_distribution
25 using boost::math::inverse_chi_squared_distribution;
26 using boost::math::cdf;
27 using boost::math::pdf;
29 // Use Inverse Gamma distribution to check their relationship:
30 // inverse_chi_squared<>(v) == inverse_gamma<>(v / 2., 0.5)
31 #include <boost/math/distributions/inverse_gamma.hpp> // for inverse_gamma_distribution
32 using boost::math::inverse_gamma_distribution;
33 using boost::math::inverse_gamma;
34 // using ::boost::math::cdf;
35 // using ::boost::math::pdf;
37 #include <boost/math/special_functions/gamma.hpp>
38 using boost::math::tgamma; // for naive pdf.
44 using std::numeric_limits; // for epsilon.
46 template <class RealType>
47 RealType naive_pdf(RealType df, RealType scale, RealType x)
48 { // Formula from Wikipedia
49 using namespace std; // For ADL of std functions.
50 using boost::math::tgamma;
51 RealType result = pow(scale * df/2, df/2) * exp(-df * scale/(2 * x));
52 result /= tgamma(df/2) * pow(x, 1 + df/2);
56 // Test using a spot value from some other reference source,
57 // in this case test values from output from R provided by Thomas Mang,
58 // and Wolfram Mathematica by Mark Coleman.
60 template <class RealType>
62 RealType degrees_of_freedom, // degrees_of_freedom,
63 RealType scale, // scale,
64 RealType x, // random variate x,
65 RealType pd, // expected pdf,
66 RealType P, // expected CDF,
67 RealType Q, // expected complement of CDF,
68 RealType tol) // test tolerance.
70 boost::math::inverse_chi_squared_distribution<RealType> dist(degrees_of_freedom, scale);
72 BOOST_CHECK_CLOSE_FRACTION
73 ( // Compare to expected PDF.
74 pdf(dist, x), // calculated.
78 BOOST_CHECK_CLOSE_FRACTION( // Compare to naive pdf formula (probably less accurate).
79 pdf(dist, x), naive_pdf(dist.degrees_of_freedom(), dist.scale(), x), tol);
81 BOOST_CHECK_CLOSE_FRACTION( // Compare to expected CDF.
82 cdf(dist, x), P, tol);
84 if((P < 0.999) && (Q < 0.999))
85 { // We can only check this if P is not too close to 1,
86 // so that we can guarantee Q is accurate:
87 BOOST_CHECK_CLOSE_FRACTION(
88 cdf(complement(dist, x)), Q, tol); // 1 - cdf
89 BOOST_CHECK_CLOSE_FRACTION(
90 quantile(dist, P), x, tol); // quantile(cdf) = x
91 BOOST_CHECK_CLOSE_FRACTION(
92 quantile(complement(dist, Q)), x, tol); // quantile(complement(1 - cdf)) = x
96 template <class RealType> // Any floating-point type RealType.
97 void test_spots(RealType)
99 // Basic sanity checks, some test data is to six decimal places only,
100 // so set tolerance to 0.000001 (expressed as a percentage = 0.0001%).
102 RealType tolerance = 0.000001f;
103 cout << "Tolerance = " << tolerance * 100 << "%." << endl;
105 // This test values from output from geoR (17 decimal digits) guided by Thomas Mang.
106 test_spot(static_cast<RealType>(2), static_cast<RealType>(1./2.),
107 // degrees_of_freedom, default scale = 1/df.
108 static_cast<RealType>(1.L), // x.
109 static_cast<RealType>(0.30326532985631671L), // pdf.
110 static_cast<RealType>(0.60653065971263365L), // cdf.
111 static_cast<RealType>(1 - 0.606530659712633657L), // cdf complement.
115 // Tests from Mark Coleman & Georgi Boshnakov using Wolfram Mathematica.
116 test_spot(static_cast<RealType>(10), static_cast<RealType>(0.1L), // degrees_of_freedom, scale
117 static_cast<RealType>(0.2), // x
118 static_cast<RealType>(1.6700235722635659824529759616528281217001163943570L), // pdf
119 static_cast<RealType>(0.89117801891415124234834646836872197623907651175353L), // cdf
120 static_cast<RealType>(1 - 0.89117801891415127L), // cdf complement
124 test_spot(static_cast<RealType>(10), static_cast<RealType>(0.1L), // degrees_of_freedom, scale
125 static_cast<RealType>(0.5), // x
126 static_cast<RealType>(0.03065662009762021L), // pdf
127 static_cast<RealType>(0.99634015317265628765454354418728984933240514654437L), // cdf
128 static_cast<RealType>(1 - 0.99634015317265628765454354418728984933240514654437L), // cdf complement
133 test_spot(static_cast<RealType>(10), static_cast<RealType>(2), // degrees_of_freedom, scale
134 static_cast<RealType>(0.5), // x
135 static_cast<RealType>(0.00054964096598361569L), // pdf
136 static_cast<RealType>(0.000016944743930067383903707995865261004246785511612700L), // cdf
137 static_cast<RealType>(1 - 0.000016944743930067383903707995865261004246785511612700L), // cdf complement
141 // Check some bad parameters to the distribution cause expected exception to be thrown.
142 BOOST_CHECK_THROW(boost::math::inverse_chi_squared_distribution<RealType> ichsqbad1(-1), std::domain_error); // negative degrees_of_freedom.
143 BOOST_CHECK_THROW(boost::math::inverse_chi_squared_distribution<RealType> ichsqbad2(1, -1), std::domain_error); // negative scale.
144 BOOST_CHECK_THROW(boost::math::inverse_chi_squared_distribution<RealType> ichsqbad3(-1, -1), std::domain_error); // negative scale and degrees_of_freedom.
146 inverse_chi_squared_distribution<RealType> ichsq;
148 if(std::numeric_limits<RealType>::has_infinity)
150 BOOST_CHECK_THROW(pdf(ichsq, +std::numeric_limits<RealType>::infinity()), std::domain_error); // x = + infinity, pdf = 0
151 BOOST_CHECK_THROW(pdf(ichsq, -std::numeric_limits<RealType>::infinity()), std::domain_error); // x = - infinity, pdf = 0
152 BOOST_CHECK_THROW(cdf(ichsq, +std::numeric_limits<RealType>::infinity()),std::domain_error ); // x = + infinity, cdf = 1
153 BOOST_CHECK_THROW(cdf(ichsq, -std::numeric_limits<RealType>::infinity()), std::domain_error); // x = - infinity, cdf = 0
154 BOOST_CHECK_THROW(cdf(complement(ichsq, +std::numeric_limits<RealType>::infinity())), std::domain_error); // x = + infinity, c cdf = 0
155 BOOST_CHECK_THROW(cdf(complement(ichsq, -std::numeric_limits<RealType>::infinity())), std::domain_error); // x = - infinity, c cdf = 1
156 BOOST_CHECK_THROW(boost::math::inverse_chi_squared_distribution<RealType> nbad1(std::numeric_limits<RealType>::infinity(), static_cast<RealType>(1)), std::domain_error); // +infinite mean
157 BOOST_CHECK_THROW(boost::math::inverse_chi_squared_distribution<RealType> nbad1(-std::numeric_limits<RealType>::infinity(), static_cast<RealType>(1)), std::domain_error); // -infinite mean
158 BOOST_CHECK_THROW(boost::math::inverse_chi_squared_distribution<RealType> nbad1(static_cast<RealType>(0), std::numeric_limits<RealType>::infinity()), std::domain_error); // infinite sd
161 if (std::numeric_limits<RealType>::has_quiet_NaN)
162 { // If no longer allow x or p to be NaN, then these tests should throw.
163 BOOST_CHECK_THROW(pdf(ichsq, +std::numeric_limits<RealType>::quiet_NaN()), std::domain_error); // x = NaN
164 BOOST_CHECK_THROW(cdf(ichsq, +std::numeric_limits<RealType>::quiet_NaN()), std::domain_error); // x = NaN
165 BOOST_CHECK_THROW(cdf(complement(ichsq, +std::numeric_limits<RealType>::quiet_NaN())), std::domain_error); // x = + infinity
166 BOOST_CHECK_THROW(quantile(ichsq, std::numeric_limits<RealType>::quiet_NaN()), std::domain_error); // p = + quiet_NaN
167 BOOST_CHECK_THROW(quantile(complement(ichsq, std::numeric_limits<RealType>::quiet_NaN())), std::domain_error); // p = + quiet_NaN
169 // Spot check for pdf using 'naive pdf' function
170 for(RealType x = 0.5; x < 5; x += 0.5)
172 BOOST_CHECK_CLOSE_FRACTION(
173 pdf(inverse_chi_squared_distribution<RealType>(5, 6), x),
174 naive_pdf(RealType(5), RealType(6), x),
176 } // Spot checks for parameters:
178 RealType tol_2eps = boost::math::tools::epsilon<RealType>() * 2; // 2 eps as a fraction.
179 inverse_chi_squared_distribution<RealType> dist51(5, 1);
180 inverse_chi_squared_distribution<RealType> dist52(5, 2);
181 inverse_chi_squared_distribution<RealType> dist31(3, 1);
182 inverse_chi_squared_distribution<RealType> dist111(11, 1);
183 // 11 mean 0.10000000000000001, variance 0.0011111111111111111, sd 0.033333333333333333
185 using namespace std; // ADL of std names.
186 using namespace boost::math;
188 inverse_chi_squared_distribution<RealType> dist10(10);
189 // mean, variance etc
190 BOOST_CHECK_CLOSE_FRACTION(mean(dist10), static_cast<RealType>(0.125), tol_2eps);
191 BOOST_CHECK_CLOSE_FRACTION(variance(dist10), static_cast<RealType>(0.0052083333333333333333333333333333333333333333333333L), tol_2eps);
192 BOOST_CHECK_CLOSE_FRACTION(mode(dist10), static_cast<RealType>(0.08333333333333333333333333333333333333333333333L), tol_2eps);
193 BOOST_CHECK_CLOSE_FRACTION(median(dist10), static_cast<RealType>(0.10704554778227709530244586234274024205738435512468L), tol_2eps);
194 BOOST_CHECK_CLOSE_FRACTION(cdf(dist10, median(dist10)), static_cast<RealType>(0.5L), tol_2eps);
195 BOOST_CHECK_CLOSE_FRACTION(skewness(dist10), static_cast<RealType>(3.4641016151377545870548926830117447338856105076208L), tol_2eps);
196 BOOST_CHECK_CLOSE_FRACTION(kurtosis(dist10), static_cast<RealType>(45), tol_2eps);
197 BOOST_CHECK_CLOSE_FRACTION(kurtosis_excess(dist10), static_cast<RealType>(45-3), tol_2eps);
199 tol_2eps = boost::math::tools::epsilon<RealType>() * 2; // 2 eps as a percentage.
201 // Special and limit cases:
203 RealType mx = (std::numeric_limits<RealType>::max)();
204 RealType mi = (std::numeric_limits<RealType>::min)();
207 pdf(inverse_chi_squared_distribution<RealType>(1),
208 static_cast<RealType>(mx)), // max()
209 static_cast<RealType>(0)
213 pdf(inverse_chi_squared_distribution<RealType>(1),
214 static_cast<RealType>(mi)), // min()
215 static_cast<RealType>(0)
219 pdf(inverse_chi_squared_distribution<RealType>(1), static_cast<RealType>(0)), static_cast<RealType>(0));
221 pdf(inverse_chi_squared_distribution<RealType>(3), static_cast<RealType>(0))
222 , static_cast<RealType>(0.0f));
224 cdf(inverse_chi_squared_distribution<RealType>(1), static_cast<RealType>(0))
225 , static_cast<RealType>(0.0f));
227 cdf(inverse_chi_squared_distribution<RealType>(2), static_cast<RealType>(0))
228 , static_cast<RealType>(0.0f));
230 cdf(inverse_chi_squared_distribution<RealType>(3L), static_cast<RealType>(0L))
231 , static_cast<RealType>(0));
233 cdf(complement(inverse_chi_squared_distribution<RealType>(1), static_cast<RealType>(0)))
234 , static_cast<RealType>(1));
236 cdf(complement(inverse_chi_squared_distribution<RealType>(2), static_cast<RealType>(0)))
237 , static_cast<RealType>(1));
239 cdf(complement(inverse_chi_squared_distribution<RealType>(3), static_cast<RealType>(0)))
240 , static_cast<RealType>(1));
244 inverse_chi_squared_distribution<RealType>(static_cast<RealType>(-1)), // degrees_of_freedom negative.
245 static_cast<RealType>(1)), std::domain_error
249 inverse_chi_squared_distribution<RealType>(static_cast<RealType>(8)),
250 static_cast<RealType>(-1)), std::domain_error
254 inverse_chi_squared_distribution<RealType>(static_cast<RealType>(-1)),
255 static_cast<RealType>(1)), std::domain_error
259 inverse_chi_squared_distribution<RealType>(static_cast<RealType>(8)),
260 static_cast<RealType>(-1)), std::domain_error
264 inverse_chi_squared_distribution<RealType>(static_cast<RealType>(-1)),
265 static_cast<RealType>(1))), std::domain_error
269 inverse_chi_squared_distribution<RealType>(static_cast<RealType>(8)),
270 static_cast<RealType>(-1))), std::domain_error
274 inverse_chi_squared_distribution<RealType>(static_cast<RealType>(-1)),
275 static_cast<RealType>(0.5)), std::domain_error
279 inverse_chi_squared_distribution<RealType>(static_cast<RealType>(8)),
280 static_cast<RealType>(-1)), std::domain_error
284 inverse_chi_squared_distribution<RealType>(static_cast<RealType>(8)),
285 static_cast<RealType>(1.1)), std::domain_error
289 inverse_chi_squared_distribution<RealType>(static_cast<RealType>(-1)),
290 static_cast<RealType>(0.5))), std::domain_error
294 inverse_chi_squared_distribution<RealType>(static_cast<RealType>(8)),
295 static_cast<RealType>(-1))), std::domain_error
299 inverse_chi_squared_distribution<RealType>(static_cast<RealType>(8)),
300 static_cast<RealType>(1.1))), std::domain_error
302 } // template <class RealType>void test_spots(RealType)
305 int test_main(int, char* [])
307 BOOST_MATH_CONTROL_FP;
309 double tol_few_eps = numeric_limits<double>::epsilon() * 4;
311 // Check that can generate inverse_chi_squared distribution using the two convenience methods:
312 // inverse_chi_squared_distribution; // with default parameters, degrees_of_freedom = 1, scale - 1
313 using boost::math::inverse_chi_squared;
315 // Some constructor tests using default double.
316 double tol4eps = boost::math::tools::epsilon<double>() * 4; // 4 eps as a fraction.
318 inverse_chi_squared ichsqdef; // Using typedef and both default parameters.
320 BOOST_CHECK_EQUAL(ichsqdef.degrees_of_freedom(), 1.); // df == 1
321 BOOST_CHECK_EQUAL(ichsqdef.scale(), 1); // scale == 1./df
322 BOOST_CHECK_CLOSE_FRACTION(pdf(ichsqdef, 1), 0.24197072451914330, tol4eps);
323 BOOST_CHECK_CLOSE_FRACTION(pdf(ichsqdef, 9), 0.013977156581221969, tol4eps);
325 inverse_chi_squared_distribution<double> ichisq102(10., 2); // Both parameters specified.
326 BOOST_CHECK_EQUAL(ichisq102.degrees_of_freedom(), 10.); // Check both parameters stored OK.
327 BOOST_CHECK_EQUAL(ichisq102.scale(), 2.); // Check both parameters stored OK.
329 inverse_chi_squared_distribution<double> ichisq10(10.); // Only df parameter specified (unscaled).
330 BOOST_CHECK_EQUAL(ichisq10.degrees_of_freedom(), 10.); // Check parameter stored.
331 BOOST_CHECK_EQUAL(ichisq10.scale(), 0.1); // Check default scale = 1/df = 1/10 = 0.1
332 BOOST_CHECK_CLOSE_FRACTION(pdf(ichisq10, 1), 0.00078975346316749169, tol4eps);
333 BOOST_CHECK_CLOSE_FRACTION(pdf(ichisq10, 10), 0.0000000012385799798186384, tol4eps);
335 BOOST_CHECK_CLOSE_FRACTION(mode(ichisq10), 0.0833333333333333333333333333333333333333, tol4eps);
336 // nu * xi / nu + 2 = 10 * 0.1 / (10 + 2) = 1/12 = 0.0833333...
337 // mode is not defined in Mathematica.
338 // See Discussion section http://en.wikipedia.org/wiki/Talk:Scaled-inverse-chi-square_distribution
339 // for origin of this formula.
341 inverse_chi_squared_distribution<double> ichisq5(5.); // // Only df parameter specified.
342 BOOST_CHECK_EQUAL(ichisq5.degrees_of_freedom(), 5.); // check parameter stored.
343 BOOST_CHECK_EQUAL(ichisq5.scale(), 1./5.); // check default is 1/df
344 BOOST_CHECK_CLOSE_FRACTION(pdf(ichisq5, 0.2), 3.0510380337346841, tol4eps);
345 BOOST_CHECK_CLOSE_FRACTION(cdf(ichisq5, 0.5), 0.84914503608460956, tol4eps);
346 BOOST_CHECK_CLOSE_FRACTION(cdf(complement(ichisq5, 0.5)), 1 - 0.84914503608460956, tol4eps);
348 BOOST_CHECK_CLOSE_FRACTION(quantile(ichisq5, 0.84914503608460956), 0.5, tol4eps*100);
349 BOOST_CHECK_CLOSE_FRACTION(quantile(complement(ichisq5, 1. - 0.84914503608460956)), 0.5, tol4eps*100);
351 // Check mean, etc spot values.
352 inverse_chi_squared_distribution<double> ichisq81(8., 1.); // degrees_of_freedom = 5, scale = 1
353 BOOST_CHECK_CLOSE_FRACTION(mean(ichisq81),1.33333333333333333333333333333333333333333, tol4eps);
354 BOOST_CHECK_CLOSE_FRACTION(variance(ichisq81), 0.888888888888888888888888888888888888888888888, tol4eps);
355 BOOST_CHECK_CLOSE_FRACTION(skewness(ichisq81), 2 * std::sqrt(8.), tol4eps);
356 inverse_chi_squared_distribution<double> ichisq21(2., 1.);
357 BOOST_CHECK_CLOSE_FRACTION(mode(ichisq21), 0.5, tol4eps);
358 BOOST_CHECK_CLOSE_FRACTION(median(ichisq21), 1.4426950408889634, tol4eps);
360 inverse_chi_squared ichsq4(4.); // Using typedef and degrees_of_freedom parameter (and default scale = 1/df).
361 BOOST_CHECK_EQUAL(ichsq4.degrees_of_freedom(), 4.); // df == 4.
362 BOOST_CHECK_EQUAL(ichsq4.scale(), 0.25); // scale == 1 /df == 1/4.
364 inverse_chi_squared ichsq32(3, 2);
365 BOOST_CHECK_EQUAL(ichsq32.degrees_of_freedom(), 3.); // df == 3.
366 BOOST_CHECK_EQUAL(ichsq32.scale(), 2); // scale == 2
368 inverse_chi_squared ichsq11(1, 1); // Using explicit degrees_of_freedom parameter, and default scale = 1).
369 BOOST_CHECK_CLOSE_FRACTION(mode(ichsq11), 0.3333333333333333333333333333333333333333, tol4eps);
370 // (1 * 1)/ (1 + 2) = 1/3 using Wikipedia nu * xi /(nu + 2)
371 BOOST_CHECK_EQUAL(ichsq11.degrees_of_freedom(), 1.); // df == 1 (default).
372 BOOST_CHECK_EQUAL(ichsq11.scale(), 1.); // scale == 1.
374 // Used to find some 'exact' values for testing mean, variance ...
375 // First with scale fixed at unity (Wikipedia definition 1)
376 cout << "df scale mean variance sd median" << endl;
377 for (int degrees_of_freedom = 8; degrees_of_freedom < 30; degrees_of_freedom++)
379 inverse_chi_squared ichisq(degrees_of_freedom, 1);
381 cout << degrees_of_freedom << " " << 1 << " " << mean(ichisq) << ' '
382 << variance(ichisq) << ' ' << standard_deviation(ichisq)
383 << ' ' << median(ichisq) << endl;
386 // Default scale = 1 / df
387 cout << "|\n" << "df scale mean variance sd median" << endl;
388 for (int degrees_of_freedom = 8; degrees_of_freedom < 30; degrees_of_freedom++)
390 inverse_chi_squared ichisq(degrees_of_freedom);
392 cout << degrees_of_freedom << " " << 1./degrees_of_freedom << " " << mean(ichisq) << ' '
393 << variance(ichisq) << ' ' << standard_deviation(ichisq)
394 << ' ' << median(ichisq) << endl;
397 inverse_chi_squared_distribution<> ichisq14(14, 1); // Using default RealType double.
398 BOOST_CHECK_CLOSE_FRACTION(mean(ichisq14), 1.166666666666666666666666666666666666666666666, tol4eps);
399 BOOST_CHECK_CLOSE_FRACTION(variance(ichisq14), 0.272222222222222222222222222222222222222222222, tol4eps);
401 inverse_chi_squared_distribution<> ichisq121(12); // Using default RealType double.
402 BOOST_CHECK_CLOSE_FRACTION(mean(ichisq121), 0.1, tol4eps);
403 BOOST_CHECK_CLOSE_FRACTION(variance(ichisq121), 0.0025, tol4eps);
404 BOOST_CHECK_CLOSE_FRACTION(standard_deviation(ichisq121), 0.05, tol4eps);
406 // and "using boost::math::inverse_chi_squared_distribution;".
407 inverse_chi_squared_distribution<> ichsq23(2., 3.); // Using default RealType double.
408 BOOST_CHECK_EQUAL(ichsq23.degrees_of_freedom(), 2.); //
409 BOOST_CHECK_EQUAL(ichsq23.scale(), 3.); //
410 BOOST_CHECK_THROW(mean(ichsq23), std::domain_error); // Degrees of freedom (nu) must be > 2
411 BOOST_CHECK_THROW(variance(ichsq23), std::domain_error); // Degrees of freedom (nu) must be > 4
412 BOOST_CHECK_THROW(skewness(ichsq23), std::domain_error); // Degrees of freedom (nu) must be > 6
413 BOOST_CHECK_THROW(kurtosis_excess(ichsq23), std::domain_error); // Degrees of freedom (nu) must be > 8
415 { // Check relationship between inverse gamma and inverse chi_squared distributions.
416 using boost::math::inverse_gamma_distribution;
420 double alpha = df/2; // aka inv_gamma shape
421 double beta = scale /2; // inv_gamma scale.
423 inverse_gamma_distribution<> ig(alpha, beta);
425 inverse_chi_squared_distribution<> ichsq(df, 1./df); // == default scale.
426 BOOST_CHECK_EQUAL(pdf(ichsq, 0), 0); // Special case of zero x.
429 BOOST_CHECK_EQUAL(pdf(ig, x), pdf(ichsq, x)); // inv_gamma compared to inv_chisq
430 BOOST_CHECK_EQUAL(cdf(ichsq, 0), 0); // Special case of zero.
431 BOOST_CHECK_EQUAL(cdf(ig, x), cdf(ichsq, x)); // invgamma == invchisq
433 // Test pdf by comparing using naive_pdf with relation to inverse gamma distribution
434 // wikipedia http://en.wikipedia.org/wiki/Scaled-inverse-chi-square_distribution related distributions.
435 // So if naive_pdf is correct, inverse_chi_squared_distribution should agree.
437 BOOST_CHECK_CLOSE_FRACTION(naive_pdf(df, scale, x), pdf(ichsq11, x), tol_few_eps);
439 //inverse_gamma_distribution<> igd(df/2, (df * scale)/2);
440 inverse_gamma_distribution<> igd11(df/2, df * scale/2);
441 BOOST_CHECK_CLOSE_FRACTION(naive_pdf(df, scale, x), pdf(igd11, x), tol_few_eps);
442 BOOST_CHECK_CLOSE_FRACTION(naive_pdf(df, scale, x), pdf(ichsq11, x), tol_few_eps);
445 inverse_gamma_distribution<> igd21(df/2, df * scale/2);
446 inverse_chi_squared_distribution<> ichsq21(df, scale);
447 BOOST_CHECK_CLOSE_FRACTION(naive_pdf(df, scale, x), pdf(igd21, x), tol_few_eps); // 0.54134113294645081 OK
448 BOOST_CHECK_CLOSE_FRACTION(naive_pdf(df, scale, x), pdf(ichsq21, x), tol_few_eps);
451 inverse_gamma_distribution<> igd22(df/2, df * scale/2);
452 inverse_chi_squared_distribution<> ichsq22(df, scale);
453 BOOST_CHECK_CLOSE_FRACTION(naive_pdf(df, scale, x), pdf(igd22, x), tol_few_eps);
454 BOOST_CHECK_CLOSE_FRACTION(naive_pdf(df, scale, x), pdf(ichsq22, x), tol_few_eps);
457 // Check using float.
458 inverse_chi_squared_distribution<float> igf23(1.f, 2.f); // Using explicit RealType float.
459 BOOST_CHECK_EQUAL(igf23.degrees_of_freedom(), 1.f); //
460 BOOST_CHECK_EQUAL(igf23.scale(), 2.f); //
462 // Check throws from bad parameters.
463 inverse_chi_squared ig051(0.5, 1.); // degrees_of_freedom < 1, so wrong for mean.
464 BOOST_CHECK_THROW(mean(ig051), std::domain_error);
465 inverse_chi_squared ig191(1.9999, 1.); // degrees_of_freedom < 2, so wrong for variance.
466 BOOST_CHECK_THROW(variance(ig191), std::domain_error);
467 inverse_chi_squared ig291(2.9999, 1.); // degrees_of_freedom < 3, so wrong for skewness.
468 BOOST_CHECK_THROW(skewness(ig291), std::domain_error);
469 inverse_chi_squared ig391(3.9999, 1.); // degrees_of_freedom < 1, so wrong for kurtosis and kurtosis_excess.
470 BOOST_CHECK_THROW(kurtosis(ig391), std::domain_error);
471 BOOST_CHECK_THROW(kurtosis_excess(ig391), std::domain_error);
473 inverse_chi_squared ig102(10, 2); // Wolfram.com/ page 2, quantile = 2.96859.
474 //http://reference.wolfram.com/mathematica/ref/InverseChiSquareDistribution.html
475 BOOST_CHECK_CLOSE_FRACTION(quantile(ig102, 0.75), 2.96859, 0.000001);
476 BOOST_CHECK_CLOSE_FRACTION(cdf(ig102, 2.96859), 0.75 , 0.000001);
477 BOOST_CHECK_CLOSE_FRACTION(cdf(complement(ig102, 2.96859)), 1 - 0.75 , 0.00001);
478 BOOST_CHECK_CLOSE_FRACTION(quantile(complement(ig102, 1 - 0.75)), 2.96859, 0.000001);
480 // Basic sanity-check spot values.
481 // (Parameter value, arbitrarily zero, only communicates the floating point type).
482 test_spots(0.0F); // Test float. OK at decdigits = 0 tolerance = 0.0001 %
483 test_spots(0.0); // Test double. OK at decdigits 7, tolerance = 1e07 %
484 #ifndef BOOST_MATH_NO_LONG_DOUBLE_MATH_FUNCTIONS
485 test_spots(0.0L); // Test long double.
486 #if !BOOST_WORKAROUND(__BORLANDC__, BOOST_TESTED_AT(0x0582))
487 test_spots(boost::math::concepts::real_concept(0.)); // Test real concept.
490 std::cout << "<note>The long double tests have been disabled on this platform "
491 "either because the long double overloads of the usual math functions are "
492 "not available at all, or because they are too inaccurate for these tests "
493 "to pass.</note>" << std::cout;
498 } // int test_main(int, char* [])