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| <div class="titlepage"><div><div><h3 class="title"> |
| <a name="math_toolkit.main_overview.faq"></a><a class="link" href="faq.html" title="Frequently Asked Questions FAQ"> Frequently Asked Questions |
| FAQ</a> |
| </h3></div></div></div> |
| <div class="orderedlist"><ol type="1"> |
| <li> |
| <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> |
| <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> |
| <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> |
| <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/dist_ref/nmp.html#math.dist.cdf">Cumulative Distribution Function</a>, |
| <a class="link" href="../dist/dist_ref/nmp.html#math.dist.pdf">Probability Density Function</a>, <a class="link" href="../dist/dist_ref/nmp.html#math.dist.quantile">Quantile</a>, <a class="link" href="../dist/dist_ref/nmp.html#math.dist.hazard">Hazard |
| Function</a>, <a class="link" href="../dist/dist_ref/nmp.html#math.dist.chf">Cumulative Hazard Function</a>, |
| <a class="link" href="../dist/dist_ref/nmp.html#math.dist.mean">mean</a>, <a class="link" href="../dist/dist_ref/nmp.html#math.dist.median">median</a>, |
| <a class="link" href="../dist/dist_ref/nmp.html#math.dist.mode">mode</a>, <a class="link" href="../dist/dist_ref/nmp.html#math.dist.variance">variance</a>, |
| <a class="link" href="../dist/dist_ref/nmp.html#math.dist.sd">standard deviation</a>, <a class="link" href="../dist/dist_ref/nmp.html#math.dist.skewness">skewness</a>, |
| <a class="link" href="../dist/dist_ref/nmp.html#math.dist.kurtosis">kurtosis</a>, <a class="link" href="../dist/dist_ref/nmp.html#math.dist.kurtosis_excess">kurtosis_excess</a>, |
| <a class="link" href="../dist/dist_ref/nmp.html#math.dist.range">range</a> and <a class="link" href="../dist/dist_ref/nmp.html#math.dist.support">support</a>. |
| </li> |
| <li> |
| <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> |
| <span class="emphasis"><em>I am a C# (Basic? F# FORTRAN? Other CLI?) programmer. Can I |
| use Boost.Math with C#?</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> |
| <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="Policies">Policies</a>. |
| But if, very probably, the default behaviour suits you, you don't need |
| to know more. |
| </li> |
| <li> |
| <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="../policy/pol_ref/error_handling_policies.html" title="Error Handling Policies">error |
| handling policies</a> and <a class="link" href="../policy/pol_tutorial/user_def_err_pol.html" title="Calling User Defined Error Handlers">user |
| error handling</a> and many examples. |
| </li> |
| <li> |
| <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#overflow_error">overflow_error</a> |
| and <a class="link" href="../policy/pol_ref/error_handling_policies.html" title="Error Handling Policies">error |
| handling policies</a> and several examples. |
| </li> |
| <li> |
| <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#domain_error">domain_error</a>, |
| <a class="link" href="error_handling.html#overflow_error">overflow_error</a> <a class="link" href="../policy/pol_ref/error_handling_policies.html" title="Error Handling Policies">error |
| handling policies</a> <a class="link" href="../policy/pol_tutorial/user_def_err_pol.html" title="Calling User Defined Error Handlers">user |
| error handling</a> etc and examples. |
| </li> |
| <li> |
| <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="../policy/pol_tutorial/user_def_err_pol.html" title="Calling User Defined Error Handlers">user |
| error handling</a> and <a class="link" href="../policy/pol_ref/policy_defaults.html" title="Using macros to Change the Policy Defaults">changing |
| policies defaults</a> . |
| </li> |
| <li> |
| <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> |
| <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> |
| <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. You might be able to squeeze a little more accuracy |
| at the cost of runtime. |
| </li> |
| <li> |
| <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="Performance">performance</a>. |
| </li> |
| <li> |
| <span class="emphasis"><em>Where are the pre-built libraries?</em></span> <br> Good news |
| - you probably don't need any! - just #include <boost/math/distribution_you_want>. |
| 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> |
| <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> |
| </ol></div> |
| </div> |
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| <td align="left"></td> |
| <td align="right"><div class="copyright-footer">Copyright © 2006 , 2007, 2008, 2009, 2010 John Maddock, Paul A. Bristow, |
| Hubert Holin, Xiaogang Zhang, Bruno Lalande, Johan Råde, Gautam Sewani and |
| Thijs van den Berg<p> |
| Distributed under the Boost Software License, Version 1.0. (See accompanying |
| file LICENSE_1_0.txt or copy at <a href="http://www.boost.org/LICENSE_1_0.txt" target="_top">http://www.boost.org/LICENSE_1_0.txt</a>) |
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