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| <div class="titlepage"><div><div><h2 class="title" style="clear: both"> |
| <a name="math_toolkit.main_faq"></a><a class="link" href="main_faq.html" title="Frequently Asked Questions FAQ">Frequently Asked Questions FAQ</a> |
| </h2></div></div></div> |
| <div class="orderedlist"><ol class="orderedlist" type="1"> |
| <li class="listitem"> |
| <span class="emphasis"><em>I'm a FORTRAN/NAG/SPSS/SAS/Cephes/MathCad/R user and I don't |
| see where the functions like dnorm(mean, sd) are in Boost.Math?</em></span> |
| <br> Nearly all are provided, and many more like mean, skewness, quantiles, |
| complements ... but Boost.Math makes full use of C++, and it looks a bit |
| different. But do not panic! See section on construction and the many examples. |
| Briefly, the distribution is constructed with the parameters (like location |
| and scale) (things after the | in representation like P(X=k|n, p) or ; |
| in a common represention of pdf f(x; μσ<sup>2</sup>). Functions like pdf, cdf are called |
| with the name of that distribution and the random variate often called |
| x or k. For example, <code class="computeroutput"><span class="identifier">normal</span> <span class="identifier">my_norm</span><span class="special">(</span><span class="number">0</span><span class="special">,</span> <span class="number">1</span><span class="special">);</span> <span class="identifier">pdf</span><span class="special">(</span><span class="identifier">my_norm</span><span class="special">,</span> <span class="number">2.0</span><span class="special">);</span></code> |
| <br> |
| </li> |
| <li class="listitem"> |
| I'm a user of <a href="http://support.sas.com/rnd/app/da/new/probabilityfunctions.html" target="_top">New |
| SAS Functions for Computing Probabilities</a>. <br> You will find |
| the interface more familar, but to be able to select a distribution (perhaps |
| using a string) see the Extras/Future Directions section, and /boost/libs/math/dot_net_example/boost_math.cpp |
| for an example that is used to create a C# (C sharp) utility (that you |
| might also find useful): see <a href="http://sourceforge.net/projects/distexplorer/" target="_top">Statistical |
| Distribution Explorer</a>.<br> |
| </li> |
| <li class="listitem"> |
| <span class="emphasis"><em>I'm allegic to reading manuals and prefer to learn from examples.</em></span><br> |
| Fear not - you are not alone! Many examples are available for functions |
| and distributions. Some are referenced directly from the text. Others can |
| be found at \boost_latest_release\libs\math\example. If you are a Visual |
| Studio user, you should be able to create projects from each of these, |
| making sure that the Boost library is in the include directories list. |
| </li> |
| <li class="listitem"> |
| <span class="emphasis"><em>How do I make sure that the Boost library is in the Visual Studio |
| include directories list?</em></span><br> You can add an include path, |
| for example, your Boost place /boost-latest_release, for example <code class="computeroutput"><span class="identifier">X</span><span class="special">:/</span><span class="identifier">boost_1_45_0</span><span class="special">/</span></code> if you have a separate partition X for |
| Boost releases. Or you can use an environment variable BOOST_ROOT set to |
| your Boost place, and include that. Visual Studio before 2010 provided |
| Tools, Options, VC++ Directories to control directories: Visual Studio |
| 2010 instead provides property sheets to assist. You may find it convenient |
| to create a new one adding \boost-latest_release; to the existing include |
| items in $(IncludePath). |
| </li> |
| <li class="listitem"> |
| <span class="emphasis"><em>I'm a FORTRAN/NAG/SPSS/SAS/Cephes/MathCad/R user and I don't |
| see where the properties like mean, median, mode, variance, skewness of |
| distributions are in Boost.Math?</em></span><br> They are all available |
| (if defined for the parameters with which you constructed the distribution) |
| via <a class="link" href="dist_ref/nmp.html#math_toolkit.dist_ref.nmp.cdf">Cumulative Distribution |
| Function</a>, <a class="link" href="dist_ref/nmp.html#math_toolkit.dist_ref.nmp.pdf">Probability |
| Density Function</a>, <a class="link" href="dist_ref/nmp.html#math_toolkit.dist_ref.nmp.quantile">Quantile</a>, |
| <a class="link" href="dist_ref/nmp.html#math_toolkit.dist_ref.nmp.hazard">Hazard Function</a>, |
| <a class="link" href="dist_ref/nmp.html#math_toolkit.dist_ref.nmp.chf">Cumulative Hazard Function</a>, |
| <a class="link" href="dist_ref/nmp.html#math_toolkit.dist_ref.nmp.mean">mean</a>, <a class="link" href="dist_ref/nmp.html#math_toolkit.dist_ref.nmp.median">median</a>, |
| <a class="link" href="dist_ref/nmp.html#math_toolkit.dist_ref.nmp.mode">mode</a>, <a class="link" href="dist_ref/nmp.html#math_toolkit.dist_ref.nmp.variance">variance</a>, |
| <a class="link" href="dist_ref/nmp.html#math_toolkit.dist_ref.nmp.sd">standard deviation</a>, |
| <a class="link" href="dist_ref/nmp.html#math_toolkit.dist_ref.nmp.skewness">skewness</a>, <a class="link" href="dist_ref/nmp.html#math_toolkit.dist_ref.nmp.kurtosis">kurtosis</a>, <a class="link" href="dist_ref/nmp.html#math_toolkit.dist_ref.nmp.kurtosis_excess">kurtosis_excess</a>, |
| <a class="link" href="dist_ref/nmp.html#math_toolkit.dist_ref.nmp.range">range</a> and <a class="link" href="dist_ref/nmp.html#math_toolkit.dist_ref.nmp.support">support</a>. |
| </li> |
| <li class="listitem"> |
| <span class="emphasis"><em>I am a C programmer. Can I user Boost.Math with C?</em></span><br> |
| Yes you can, including all the special functions, and TR1 functions like |
| isnan. They appear as C functions, by being declared as "extern C". |
| </li> |
| <li class="listitem"> |
| <span class="emphasis"><em>I am a C# (Basic? F# FORTRAN? Other CLI?) programmer. Can I use |
| Boost.Math with C#? (or ...)?</em></span> <br> Yes you can, including |
| all the special functions, and TR1 functions like isnan. But you <span class="bold"><strong>must build the Boost.Math as a dynamic library (.dll) and compile |
| with the /CLI option</strong></span>. See the boost/math/dot_net_example folder |
| which contains an example that builds a simple statistical distribution |
| app with a GUI. See <a href="http://sourceforge.net/projects/distexplorer/" target="_top">Statistical |
| Distribution Explorer</a> <br> |
| </li> |
| <li class="listitem"> |
| <span class="emphasis"><em>What these "policies" things for?</em></span> <br> |
| Policies are a powerful (if necessarily complex) fine-grain mechanism that |
| allow you to customise the behaviour of the Boost.Math library according |
| to your precise needs. See <a class="link" href="../policy.html" title="Chapter 14. Policies: Controlling Precision, Error Handling etc">Policies</a>. But |
| if, very probably, the default behaviour suits you, you don't need to know |
| more. |
| </li> |
| <li class="listitem"> |
| <span class="emphasis"><em>I am a C user and expect to see global C-style<code class="computeroutput"><span class="special">::</span><span class="identifier">errno</span></code> set for overflow/errors etc?</em></span> |
| <br> You can achieve what you want - see <a class="link" href="pol_ref/error_handling_policies.html" title="Error Handling Policies">error |
| handling policies</a> and <a class="link" href="pol_tutorial/user_def_err_pol.html" title="Calling User Defined Error Handlers">user |
| error handling</a> and many examples. |
| </li> |
| <li class="listitem"> |
| <span class="emphasis"><em>I am a C user and expect to silently return a max value for overflow?</em></span> |
| <br> You (and C++ users too) can return whatever you want on overflow |
| - see <a class="link" href="error_handling.html#math_toolkit.error_handling.overflow_error">overflow_error</a> |
| and <a class="link" href="pol_ref/error_handling_policies.html" title="Error Handling Policies">error |
| handling policies</a> and several examples. |
| </li> |
| <li class="listitem"> |
| <span class="emphasis"><em>I don't want any error message for overflow etc?</em></span> |
| <br> You can control exactly what happens for all the abnormal conditions, |
| including the values returned. See <a class="link" href="error_handling.html#math_toolkit.error_handling.domain_error">domain_error</a>, |
| <a class="link" href="error_handling.html#math_toolkit.error_handling.overflow_error">overflow_error</a> |
| <a class="link" href="pol_ref/error_handling_policies.html" title="Error Handling Policies">error handling |
| policies</a> <a class="link" href="pol_tutorial/user_def_err_pol.html" title="Calling User Defined Error Handlers">user |
| error handling</a> etc and examples. |
| </li> |
| <li class="listitem"> |
| <span class="emphasis"><em>My environment doesn't allow and/or I don't want exceptions. |
| Can I still user Boost.Math?</em></span> <br> Yes but you must customise |
| the error handling: see <a class="link" href="pol_tutorial/user_def_err_pol.html" title="Calling User Defined Error Handlers">user |
| error handling</a> and <a class="link" href="pol_ref/policy_defaults.html" title="Using Macros to Change the Policy Defaults">changing |
| policies defaults</a> . |
| </li> |
| <li class="listitem"> |
| <span class="emphasis"><em>The docs are several hundreds of pages long! Can I read the docs |
| off-line or on paper?</em></span> <br> Yes - you can download the Boost |
| current release of most documentation as a zip of pdfs (including Boost.Math) |
| from Sourceforge, for example <a href="https://sourceforge.net/projects/boost/files/boost-docs/1.45.0/boost_pdf_1_45_0.tar.gz/download" target="_top">https://sourceforge.net/projects/boost/files/boost-docs/1.45.0/boost_pdf_1_45_0.tar.gz/download</a>. |
| And you can print any pages you need (or even print all pages - but be |
| warned that there are several hundred!). Both html and pdf versions are |
| highly hyperlinked. The entire Boost.Math pdf can be searched with Adobe |
| Reader, Edit, Find ... This can often find what you seek, a partial substitute |
| for a full index. |
| </li> |
| <li class="listitem"> |
| <span class="emphasis"><em>I want a compact version for an embedded application. Can I use |
| float precision?</em></span> <br> Yes - by selecting RealType template |
| parameter as float: for example normal_distribution<float> your_normal(mean, |
| sd); (But double may still be used internally, so space saving may be less |
| that you hope for). You can also change the promotion policy, but accuracy |
| might be much reduced. |
| </li> |
| <li class="listitem"> |
| <span class="emphasis"><em>I seem to get somewhat different results compared to other programs. |
| Why?</em></span> We hope Boost.Math to be more accurate: our priority is |
| accuracy (over speed). See the section on accuracy. But for evaluations |
| that require iterations there are parameters which can change the required |
| accuracy (see <a class="link" href="../policy.html" title="Chapter 14. Policies: Controlling Precision, Error Handling etc">Policies</a>). You might be able |
| to squeeze a little more (or less) accuracy at the cost of runtime. |
| </li> |
| <li class="listitem"> |
| <span class="emphasis"><em>Will my program run more slowly compared to other math functions |
| and statistical libraries?</em></span> Probably, thought not always, and |
| not by too much: our priority is accuracy. For most functions, making sure |
| you have the latest compiler version with all optimisations switched on |
| is the key to speed. For evaluations that require iteration, you may be |
| able to gain a little more speed at the expense of accuracy. See detailed |
| suggestions and results on <a class="link" href="../perf.html" title="Chapter 15. Performance">performance</a>. |
| </li> |
| <li class="listitem"> |
| <span class="emphasis"><em>How do I handle infinity and NaNs portably?</em></span> <br> |
| See <a class="link" href="fp_facets.html" title="Facets for Floating-Point Infinities and NaNs">nonfinite fp_facets</a> for |
| Facets for Floating-Point Infinities and NaNs. |
| </li> |
| <li class="listitem"> |
| <span class="emphasis"><em>Where are the pre-built libraries?</em></span> <br> Good news |
| - you probably don't need any! - just <code class="computeroutput"><span class="preprocessor">#include</span> |
| <span class="special"><</span><span class="identifier">boost</span><span class="special">/</span></code><span class="emphasis"><em>math/distribution_you_want></em></span>. |
| But in the unlikely event that you do, see <a class="link" href="building.html" title="If and How to Build a Boost.Math Library, and its Examples and Tests">building |
| libraries</a>. |
| </li> |
| <li class="listitem"> |
| <span class="emphasis"><em>I don't see the function or distribution that I want.</em></span> |
| <br> You could try an email to ask the authors - but no promises! |
| </li> |
| <li class="listitem"> |
| <span class="emphasis"><em>I need more decimal digits for values/computations.</em></span> |
| <br> You can use Boost.Math with <a href="http://www.boost.org/doc/libs/1_53_0_beta1/libs/multiprecision/doc/html/index.html" target="_top">Boost.Multiprecision</a>: |
| typically <a href="http://www.boost.org/doc/libs/1_53_0_beta1/libs/multiprecision/doc/html/boost_multiprecision/tut/floats/cpp_dec_float.html" target="_top">cpp_dec_float</a> |
| is a useful user-defined type to provide a fixed number of decimal digits, |
| usually 50 or 100. |
| </li> |
| <li class="listitem"> |
| Why can't I write something really simple like <code class="computeroutput"><span class="identifier">cpp_int</span> |
| <span class="identifier">one</span><span class="special">(</span><span class="number">1</span><span class="special">);</span> <span class="identifier">cpp_dec_float_50</span> |
| <span class="identifier">two</span><span class="special">(</span><span class="number">2</span><span class="special">);</span> <span class="identifier">one</span> |
| <span class="special">*</span> <span class="identifier">two</span><span class="special">;</span></code> Because <code class="computeroutput"><span class="identifier">cpp_int</span></code> |
| might be bigger than <code class="computeroutput"><span class="identifier">cpp_dec_float</span> |
| <span class="identifier">can</span> <span class="identifier">hold</span></code>, |
| so you must make an <span class="bold"><strong>explicit</strong></span> conversion. |
| See <a href="http://svn.boost.org/svn/boost/trunk/libs/multiprecision/doc/html/boost_multiprecision/intro.html" target="_top">mixed |
| multiprecision arithmetic</a> and <a href="http://svn.boost.org/svn/boost/trunk/libs/multiprecision/doc/html/boost_multiprecision/tut/conversions.html" target="_top">conversion</a>. |
| </li> |
| </ol></div> |
| </div> |
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| Holin, Bruno Lalande, John Maddock, Johan Råde, Gautam Sewani, Benjamin Sobotta, |
| Thijs van den Berg, Daryle Walker and Xiaogang Zhang<p> |
| Distributed under the Boost Software License, Version 1.0. (See accompanying |
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