| [section:faq Frequently Asked Questions FAQ] |
| |
| # ['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?] [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; [mu][sigma][super 2]). |
| Functions like pdf, cdf are called with the name of that distribution and the random variate often called x or k. |
| For example, `normal my_norm(0, 1); pdf(my_norm, 2.0);` [br] |
| # ['I'm allegic to reading manuals and prefer to learn from examples.][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. |
| # ['How do I make sure that the Boost library is in the Visual Studio include directories list?][br] |
| You can add an include path, for example, your Boost place /boost-latest_release, |
| for example `X:/boost_1_45_0/` 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). |
| # ['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?][br] |
| They are all available (if defined for the parameters with which you constructed the distribution) via __usual_accessors. |
| # ['I am a C programmer. Can I user Boost.Math with C?][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". |
| # ['I am a C# (Basic? F# FORTRAN? Other CLI?) programmer. Can I use Boost.Math with C#?] [br] |
| Yes you can, including all the special functions, and TR1 functions like isnan. |
| But you [*must build the Boost.Math as a dynamic library (.dll) and compile with the /CLI option]. |
| See the boost/math/dot_net_example folder which contains an example that |
| builds a simple statistical distribution app with a GUI. |
| See [@http://sourceforge.net/projects/distexplorer/ Statistical Distribution Explorer] [br] |
| # ['What these "policies" things for?] [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 __policy_section. But if, very probably, the default behaviour suits you, you don't need to know more. |
| # ['I am a C user and expect to see global C-style`::errno` set for overflow/errors etc?] [br] |
| You can achieve what you want - see __error_policy and __user_error_handling and many examples. |
| # ['I am a C user and expect to silently return a max value for overflow?] [br] |
| You (and C++ users too) can return whatever you want on overflow |
| - see __overflow_error and __error_policy and several examples. |
| # ['I don't want any error message for overflow etc?] [br] |
| You can control exactly what happens for all the abnormal conditions, including the values returned. |
| See __domain_error, __overflow_error __error_policy __user_error_handling etc and examples. |
| # ['My environment doesn't allow and/or I don't want exceptions. Can I still user Boost.Math?] [br] |
| Yes but you must customise the error handling: see __user_error_handling and __changing_policy_defaults . |
| # ['The docs are several hundreds of pages long! Can I read the docs off-line or on paper?] [br] |
| Yes - you can download the Boost current release of most documentation |
| as a zip of pdfs (including Boost.Math) from Sourceforge, |
| for example [@https://sourceforge.net/projects/boost/files/boost-docs/1.45.0/boost_pdf_1_45_0.tar.gz/download]. |
| 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. |
| # ['I want a compact version for an embedded application. Can I use float precision?] [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. |
| # ['I seem to get somewhat different results compared to other programs. Why?] |
| 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. |
| # ['Will my program run more slowly compared to other math functions and statistical libraries?] |
| 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 __performance. |
| # ['Where are the pre-built libraries?] [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 __building. |
| # ['I don't see the function or distribution that I want.] [br] |
| You could try an email to ask the authors - but no promises! |
| |
| [endsect] [/section:faq Frequently Asked Questions] |
| |
| [/ |
| Copyright 2010 John Maddock and Paul A. Bristow. |
| Distributed under the Boost Software License, Version 1.0. |
| (See accompanying file LICENSE_1_0.txt or copy at |
| http://www.boost.org/LICENSE_1_0.txt). |
| ] |
| |