NAME

       PDL::Course - A journey through PDL's documentation, from beginner to advanced.

AUTHOR, DATE

       This is written by David Mertens with edits by Daniel Carrera.

Preface

       PDL's documentation is extensive. Some sections cover deep core magic while others cover
       more usual topics like IO and numerical computation.  How are these related? Where should
       you begin?

       This document is an attempt to pull all the key PDL documentation together in a coherent
       study course, starting from the beginner level, up to the expert.

       I've broken down everything by level of expertise, and within expertise I've covered
       documentation, library, and workflow modules. The documentation modules are useful for
       what they tell you; the library modules are useful for the functions that they define for
       you; the workflow modules are useful for the way that they allow you to get your work done
       in new and different ways.

Introductory

       If you are new to PDL, these documentation modules will get you started down the right
       path for using PDL.

   Documentation
       Modules that tell you how to start using PDL.  Many of these are library modules
       technically, but they are included when you "use PDL", so I've included them for their
       documentation.

       After the first three, most of the docs listed below are rather dry. Perhaps they would be
       better summarized by tables or better synopses. You should at least scan through them to
       familiarize yourself with the basic capabilities of PDL.

       •   PDL::Philosophy, PDL::QuickStart

           A couple of brief introductions to PDL. The second one is a bit more hands-on. If you
           are new to PDL, you should start with these.

       •   PDL::Basic

           Covers basic ndarray-creation routines like "sequence", "rvals", and "logxvals" to
           name a random few.  Also covers "hist" and "transpose".

       •   PDL::Ufunc

           Explains a large collection of built-in functions which, given an N-dimension ndarray,
           will create an ndarray with N-1 dimensions.

       •   PDL::NiceSlice

           PDL came of age right around the turn of the millennium and NiceSlice came on the
           scene slightly after that.  Some of the docs still haven't caught up.  NiceSlice is
           the 'modern' way to slice and dice your ndarrays.  Read the Synopsis, then scroll down
           to The New Slicing Syntax.  After you've read to the bottom, return to and read the
           stuff at the top.

       •   PDL::Primitive

           Defines a whole slew of useful built-in functions.  These are the sorts of things that
           beginners are likely to write to the list and say, "How do I do xxx?"  You would be
           well on your way to learning the ropes after you've gotten through this document.

       •   Selections from PDL::Core

           Like PDL::Primitive, defines a large set of useful functions.  Unfortunately, some of
           the functions are quite esoteric, but are mixed in with the rest of the simple and
           easy ones.  Skim the whole document, skipping over the complicated functions for now.
           I would point out in particular the function "approx".

   Workflow
       •   The perldl or pdl2 Shell

           The Perldl Shell is a REPL (Read-Evaluate-Print-Loop, in other words, a prompt or
           shell) that allows you to work with PDL (or any Perl, for that matter) in 'real time',
           loading data from files, plotting, manipulating... Anything you can do in a script,
           you can do in the PDL Shell, with instant feedback!

   Libraries
       •   PDL

           The main workhorse module. You'll include this in nearly every PDL program you write.

Normal Usage

       The sorts of modules that you'll likely use on a normal basis in scripts or from within
       the perldl shell.  Some of these modules you may never use, but you should still be aware
       that they exist, just in case you need their functionality.

   Documentation
       •   PDL::Slices

           In addition to explaining the original slicing and dicing functions - for which you
           can usually use PDL::NiceSlice - this also covers many dimension-handling functions
           such as "mv", "xchg", and "reorder".  This also thoroughly documents the "range"
           function, which can be very powerful, and covers a number of internal functions, which
           can probably be skipped.

       •   PDL::Indexing

           This covers a lot of the deeper conceptual ground that you'll need to grasp to really
           use PDL to its full potential.  It gets more complex as you go along, so don't be
           troubled if you find yourself loosing interest half way through.  However, reading
           this document all the way through will bring you much closer to PDL enlightenment.

       •   PDL::IO

           PDL has quite a few IO modules, most of which are discussed in this summary module.

       •   PDL::Tips

           A collection of some of Tuomas's ideas for making good use of PDL.

       •   PDL::BadValues

           Explains what bad values are and how and why they are implemented.

       •   Selections from Inline::Pdlpp

           Although writing PDL::PP code is considered an Advanced topic, and is covered in the
           next section, you should be aware that it is possible (and surprisingly simple) to
           write PDL-aware code.  You needn't read the whole thing at this point, but to get some
           feel for how it works, you should read everything up through the first example.  A
           copy of this documentation is contained in PDL::PP-Inline.

       •   PDL::Objects

           Explains how to subclass an ndarray object.

       •   PDL::Index

           This was discussed in the Preface. It is an automatically generated file that lists
           all of the PDL modules on your computer. There are many modules that may be on your
           machine but which are not documented here, such as bindings to the FFTW library, or
           GSL. Give it a read!

   Libraries
       •   PDL::FFT

           PDL's own Fast Fourier Transform.  If you have FFTW, then you should probably make use
           of it; this is PDL's internal implementation and should always be available.

       •   GSL

           PDL does not have bindings for every sub-library in the GNU Scientific Library, but it
           has quite a few. If you have GSL installed on your machine then chances are decent
           that your PDL has the GSL bindings.  For a full list of the GSL bindings, check
           PDL::Index.

       •   PDL::Func

           A somewhat uniform interface to the different interpolation modules in PDL.

       •   PDL::Bad

           Includes some basic bad-value functionality, including functions to query if an
           ndarray has bad values ("isbad") and functions to set certain elements as bad
           ("setbadat" and "setbadif").  Among other places, bad values are used in
           PDL::Graphics::PLplot's xyplot to make a gap in a line plot.

       •   PDL::DiskCache

           A cool module that allows you to tie a Perl array to a collection of files on your
           disk, which will be loaded into and out of memory as ndarrays. If you find yourself
           writing scripts to process many data files, especially if that data processing is not
           necessarily in sequential order, you should consider using PDL::DiskCache.

       •   PDL::Char

           A PDL subclass that allows you to store and manipulate collections of fixed-length
           character strings using PDL.

       •   PDL::Image2D

           A whole collection of methods for manipulating images whose image data are stored in
           an ndarray.  These include methods for convolutions (smoothing), polygon fills,
           scaling, rotation, and warping, among others.

       •   PDL::ImageND

           Contains a few functions that are conceptually related to image processing, but which
           can be defined for higher-dimensional data.  For examples this module defines high-
           dimensional convolution and interpolation, among others.

       •   PDL::ImageRGB

           Defines some useful functions for working with RBG image data.  It's not very feature-
           full, but it may have something you need, and if not, you can always add more!

       •   PDL::Transform

           Creates the transform class, which allows you to create various coordinate transforms.
           For example, if you data is a collection of Cartesian coordinates, you could create a
           transform object to convert them to Spherical-Polar coordinates (although many such
           standard coordinate transformations are predefined for you, in this case it's called
           "t_spherical").

       •   PDL::Opt::Simplex

           This package states that it "implements the commonly used simplex optimization
           algorithm." I'm going to assume that if you need this algorithm then you already know
           what it is.

       •   PDL::Math

           A collection of fairly standard math functions, like the inverse trigonometric
           functions, hyperbolic functions and their inverses, and others.  This module is
           included in the standard call to "use PDL", but not in the Lite versions.

       •   PDL::Matrix

           Provides a few functions that use the standard mathematical Matrix notation of row-
           column indexing rather than the PDL-standard column-row.  It appears that this module
           has not been heavily tested with other modules, so although it should work with other
           modules, don't be surprised if something breaks when you use it (and feel free to
           offer any fixes that you may develop).

       •   PDL::MatrixOps

           Provides many standard matrix operations for ndarrays, such as computing eigenvalues,
           inverting square matrices, LU-decomposition, and solving a system of linear equations.
           Though it is not built on PDL::Matrix, it should generally work with that module.
           Also, the methods provided by this module do not depend on external libraries such as
           Slatec or GSL.

       •   PDL::Reduce

           Implements an interface to all the functions that return ndarrays with one less
           dimension (for example, "sumover"), such that they can be called by supplying their
           name, as a string.

   Workflow
       •   PDL::AutoLoader

           Enables Matlab-style autoloading.  When you call an unknown function, instead of
           complaining and croaking, PDL will go hunt around in the directories you specify in
           search of a like-named file.  Particularly useful when used with the Perldl Shell.

       •   PDL::Dbg

           Declares the "px" function, which can be handy for debugging your PDL scripts and/or
           perldl shell commands.

       •   PDL::Options

           Suppose you define a powerful, versatile function.  Chances are good that you'll
           accept the arguments in the form of a hash or hashref.  Now you face the problem of
           processing that hashref.  PDL::Options assists you in writing code to process those
           options.  (You'd think Perl would have tons of these sorts of modules lying around,
           but I couldn't find any.)  Note this module does not depend on PDL for its usage or
           installation.

       •   PDL::pdldoc

           Ever fired-up the perldl shell just to look up the help for a particular function?
           You can use "pdldoc" instead.  This shell script extracts information from the help
           index without needing to start the perldl shell.

Advanced Usage

       The sorts of modules and documentation that you'll use if you write modules that use PDL,
       or if you work on PDL maintenance.  These modules can be difficult to use, but enable you
       to tackle some of your harder problems.

       •   PDL::Lite, PDL::LiteF

           Lite-weight replacements for "use PDL", from the standpoint of namespace pollution and
           load time.

       •   Inline::Pdlpp

           This was mentioned earlier.  Before you begin reading about PDL::PP (next), you should
           remind yourself about how to use this.  Inline::Pdlpp will help you experiment with
           PDL::PP without having to go through the trouble of building a module and constructing
           makefiles (but see PDL::pptemplate for help on that).

       •   PDL::PP

           The PDL Pre-Processor, which vastly simplifies making you C or Fortran code play with
           Perl and ndarrays.  Most of PDL's basic functionality is written using PDL::PP, so if
           you're thinking about how you might integrate some numerical library written in C,
           look no further.

       •   PDL::pptemplate

           A script that automates the creation of modules that use PDL::PP, which should make
           your life as a module author a bit simpler.

       •   PDL::CallExt

           Allows you to call functions using external shared libraries.  This is an alternative
           to using PDL::PP.  The major difference between PDL::PP and PDL::CallExt is that the
           former will handle broadcasting over implicit broadcast dimensions for you, whereas
           PDL::CallExt simply calls an external function.  PDL::PP is generally the recommended
           way to interface your code with PDL, but it wouldn't be Perl if there wasn't another
           way to do it.

       •   PDL::Config

           Defines the %PDL::Config hash, which has lots of useful information pertinent to your
           PDL build.

       •   PDL::Doc

           Explanation of the PDL documentation conventions, and an interface to the PDL
           Documentation parser.  Following these guidelines when writing documentation for PDL
           functions will ensure that your wonderful documentation is accessible from the perldl
           shell and from calls to "barf".  (Did you notice that "barf" used your documentation?
           Time to reread PDL::Core...)

       •   PDL::Exporter

           A simple replacement for the standard Exporter module.  The only major difference is
           that the default imported modules are those marked ':Func'.

       •   PDL::Types

           Defines some useful functions for getting an ndarray's type, as well as getting
           information about that type.

Expert Usage

       •   PDL::Core::Dev

           Provides some decently useful functions that are pretty much only needed by the PDL
           Porters.

       •   PDL::API

           Explains how to make an ndarray by hand, from Perl or your C source code, using the
           PDL API.

       •   PDL::Internals

           Explains the nitty-gritty of the PDL data structures.  After reading this (a few times
           :), you should be able to create an ndarray completely from scratch (i.e. without
           using the PDL API).  Put a little differently, if you want to understand how PDL::PP
           works, you'll need to read this.

COPYRIGHT

       Copyright 2010 David Mertens (dcmertens.perl@gmail.com). You can distribute and/or modify
       this document under the same terms as the current Perl license.

       See: http://dev.perl.org/licenses/