1COURSE(1)             User Contributed Perl Documentation            COURSE(1)
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NAME

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

10       This is written by David Mertens with edits by Daniel Carrera.
11

Preface

13       PDL's documentation is extensive. Some sections cover deep core magic
14       while others cover more usual topics like IO and numerical computation.
15       How are these related? Where should you begin?
16
17       This document is an attempt to pull all the key PDL documentation
18       together in a coherent study course, starting from the beginner level,
19       up to the expert.
20
21       I've broken down everything by level of expertise, and within expertise
22       I've covered documentation, library, and workflow modules. The
23       documentation modules are useful for what they tell you; the library
24       modules are useful for the functions that they define for you; the
25       workflow modules are useful for the way that they allow you to get your
26       work done in new and different ways.
27

Introductory

29       If you are new to PDL, these documentation modules will get you started
30       down the right path for using PDL.
31
32   Documentation
33       Modules that tell you how to start using PDL.  Many of these are
34       library modules technically, but they are included when you "use PDL",
35       so I've included them for their documentation.
36
37       After the first three, most of the docs listed below are rather dry.
38       Perhaps they would be better summarized by tables or better synopses.
39       You should at least scan through them to familiarize yourself with the
40       basic capabilities of PDL.
41
42       •   PDL::Philosophy, PDL::QuickStart
43
44           A couple of brief introductions to PDL. The second one is a bit
45           more hands-on. If you are new to PDL, you should start with these.
46
47       •   PDL::Basic
48
49           Covers basic ndarray-creation routines like "sequence", "rvals",
50           and "logxvals" to name a random few.  Also covers "hist" and
51           "transpose".
52
53       •   PDL::Ufunc
54
55           Explains a large collection of built-in functions which, given an
56           N-dimension ndarray, will create an ndarray with N-1 dimensions.
57
58       •   PDL::NiceSlice
59
60           PDL came of age right around the turn of the millennium and
61           NiceSlice came on the scene slightly after that.  Some of the docs
62           still haven't caught up.  NiceSlice is the 'modern' way to slice
63           and dice your ndarrays.  Read the Synopsis, then scroll down to The
64           New Slicing Syntax.  After you've read to the bottom, return to and
65           read the stuff at the top.
66
67       •   PDL::Primitive
68
69           Defines a whole slew of useful built-in functions.  These are the
70           sorts of things that beginners are likely to write to the list and
71           say, "How do I do xxx?"  You would be well on your way to learning
72           the ropes after you've gotten through this document.
73
74       •   Selections from PDL::Core
75
76           Like PDL::Primitive, defines a large set of useful functions.
77           Unfortunately, some of the functions are quite esoteric, but are
78           mixed in with the rest of the simple and easy ones.  Skim the whole
79           document, skipping over the complicated functions for now.  I would
80           point out in particular the function "approx".
81
82   Workflow
83       •   The perldl or pdl2 Shell
84
85           The Perldl Shell is a REPL (Read-Evaluate-Print-Loop, in other
86           words, a prompt or shell) that allows you to work with PDL (or any
87           Perl, for that matter) in 'real time', loading data from files,
88           plotting, manipulating... Anything you can do in a script, you can
89           do in the PDL Shell, with instant feedback!
90
91   Libraries
92       •   PDL
93
94           The main workhorse module. You'll include this in nearly every PDL
95           program you write.
96

Normal Usage

98       The sorts of modules that you'll likely use on a normal basis in
99       scripts or from within the perldl shell.  Some of these modules you may
100       never use, but you should still be aware that they exist, just in case
101       you need their functionality.
102
103   Documentation
104       •   PDL::Slices
105
106           In addition to explaining the original slicing and dicing functions
107           - for which you can usually use PDL::NiceSlice - this also covers
108           many dimension-handling functions such as "mv", "xchg", and
109           "reorder".  This also thoroughly documents the "range" function,
110           which can be very powerful, and covers a number of internal
111           functions, which can probably be skipped.
112
113       •   PDL::Indexing
114
115           This covers a lot of the deeper conceptual ground that you'll need
116           to grasp to really use PDL to its full potential.  It gets more
117           complex as you go along, so don't be troubled if you find yourself
118           loosing interest half way through.  However, reading this document
119           all the way through will bring you much closer to PDL
120           enlightenment.
121
122       •   PDL::IO
123
124           PDL has quite a few IO modules, most of which are discussed in this
125           summary module.
126
127       •   PDL::Tips
128
129           A collection of some of Tuomas's ideas for making good use of PDL.
130
131       •   PDL::BadValues
132
133           Explains what bad values are and how and why they are implemented.
134
135       •   Selections from Inline::Pdlpp
136
137           Although writing PDL::PP code is considered an Advanced topic, and
138           is covered in the next section, you should be aware that it is
139           possible (and surprisingly simple) to write PDL-aware code.  You
140           needn't read the whole thing at this point, but to get some feel
141           for how it works, you should read everything up through the first
142           example.  A copy of this documentation is contained in
143           PDL::PP-Inline.
144
145       •   PDL::Objects
146
147           Explains how to subclass an ndarray object.
148
149       •   PDL::Index
150
151           This was discussed in the Preface. It is an automatically generated
152           file that lists all of the PDL modules on your computer. There are
153           many modules that may be on your machine but which are not
154           documented here, such as bindings to the FFTW library, or GSL. Give
155           it a read!
156
157   Libraries
158       •   PDL::FFT
159
160           PDL's own Fast Fourier Transform.  If you have FFTW, then you
161           should probably make use of it; this is PDL's internal
162           implementation and should always be available.
163
164       •   GSL
165
166           PDL does not have bindings for every sub-library in the GNU
167           Scientific Library, but it has quite a few. If you have GSL
168           installed on your machine then chances are decent that your PDL has
169           the GSL bindings.  For a full list of the GSL bindings, check
170           PDL::Index.
171
172       •   PDL::Func
173
174           A somewhat uniform interface to the different interpolation modules
175           in PDL.
176
177       •   PDL::Bad
178
179           Includes some basic bad-value functionality, including functions to
180           query if an ndarray has bad values ("isbad") and functions to set
181           certain elements as bad ("setbadat" and "setbadif").  Among other
182           places, bad values are used in PDL::Graphics::PLplot's xyplot to
183           make a gap in a line plot.
184
185       •   PDL::DiskCache
186
187           A cool module that allows you to tie a Perl array to a collection
188           of files on your disk, which will be loaded into and out of memory
189           as ndarrays. If you find yourself writing scripts to process many
190           data files, especially if that data processing is not necessarily
191           in sequential order, you should consider using PDL::DiskCache.
192
193       •   PDL::Char
194
195           A PDL subclass that allows you to store and manipulate collections
196           of fixed-length character strings using PDL.
197
198       •   PDL::Image2D
199
200           A whole collection of methods for manipulating images whose image
201           data are stored in an ndarray.  These include methods for
202           convolutions (smoothing), polygon fills, scaling, rotation, and
203           warping, among others.
204
205       •   PDL::ImageND
206
207           Contains a few functions that are conceptually related to image
208           processing, but which can be defined for higher-dimensional data.
209           For examples this module defines high-dimensional convolution and
210           interpolation, among others.
211
212       •   PDL::ImageRGB
213
214           Defines some useful functions for working with RBG image data.
215           It's not very feature-full, but it may have something you need, and
216           if not, you can always add more!
217
218       •   PDL::Transform
219
220           Creates the transform class, which allows you to create various
221           coordinate transforms.  For example, if you data is a collection of
222           Cartesian coordinates, you could create a transform object to
223           convert them to Spherical-Polar coordinates (although many such
224           standard coordinate transformations are predefined for you, in this
225           case it's called "t_spherical").
226
227       •   PDL::Opt::Simplex
228
229           This package states that it "implements the commonly used simplex
230           optimization algorithm." I'm going to assume that if you need this
231           algorithm then you already know what it is.
232
233       •   PDL::Math
234
235           A collection of fairly standard math functions, like the inverse
236           trigonometric functions, hyperbolic functions and their inverses,
237           and others.  This module is included in the standard call to "use
238           PDL", but not in the Lite versions.
239
240       •   PDL::Matrix
241
242           Provides a few functions that use the standard mathematical Matrix
243           notation of row-column indexing rather than the PDL-standard
244           column-row.  It appears that this module has not been heavily
245           tested with other modules, so although it should work with other
246           modules, don't be surprised if something breaks when you use it
247           (and feel free to offer any fixes that you may develop).
248
249       •   PDL::MatrixOps
250
251           Provides many standard matrix operations for ndarrays, such as
252           computing eigenvalues, inverting square matrices, LU-decomposition,
253           and solving a system of linear equations.  Though it is not built
254           on PDL::Matrix, it should generally work with that module.  Also,
255           the methods provided by this module do not depend on external
256           libraries such as Slatec or GSL.
257
258       •   PDL::Reduce
259
260           Implements an interface to all the functions that return ndarrays
261           with one less dimension (for example, "sumover"), such that they
262           can be called by suppling their name, as a string.
263
264   Workflow
265       •   PDL::AutoLoader
266
267           Enables Matlab-style autoloading.  When you call an unknown
268           function, instead of complaining and croaking, PDL will go hunt
269           around in the directories you specify in search of a like-named
270           file.  Particularly useful when used with the Perldl Shell.
271
272       •   PDL::Dbg
273
274           Declares the "px" function, which can be handy for debugging your
275           PDL scripts and/or perldl shell commands.
276
277       •   PDL::Options
278
279           Suppose you define a powerful, versatile function.  Chances are
280           good that you'll accept the arguments in the form of a hash or
281           hashref.  Now you face the problem of processing that hashref.
282           PDL::Options assists you in writing code to process those options.
283           (You'd think Perl would have tons of these sorts of modules lying
284           around, but I couldn't find any.)  Note this module does not depend
285           on PDL for its usage or installation.
286
287       •   PDL::pdldoc
288
289           Ever fired-up the perldl shell just to look up the help for a
290           particular function?  You can use "pdldoc" instead.  This shell
291           script extracts information from the help index without needing to
292           start the perldl shell.
293

Advanced Usage

295       The sorts of modules and documentation that you'll use if you write
296       modules that use PDL, or if you work on PDL maintenance.  These modules
297       can be difficult to use, but enable you to tackle some of your harder
298       problems.
299
300       •   PDL::Lite, PDL::LiteF
301
302           Lite-weight replacements for "use PDL", from the standpoint of
303           namespace pollution and load time.
304
305       •   Inline::Pdlpp
306
307           This was mentioned earlier.  Before you begin reading about PDL::PP
308           (next), you should remind yourself about how to use this.
309           Inline::Pdlpp will help you experiment with PDL::PP without having
310           to go through the trouble of building a module and constructing
311           makefiles (but see PDL::pptemplate for help on that).
312
313       •   PDL::PP
314
315           The PDL Pre-Processor, which vastly simplifies making you C or
316           Fortran code play with Perl and ndarrays.  Most of PDL's basic
317           functionality is written using PDL::PP, so if you're thinking about
318           how you might integrate some numerical library written in C, look
319           no further.
320
321       •   PDL::pptemplate
322
323           A script that automates the creation of modules that use PDL::PP,
324           which should make your life as a module author a bit simpler.
325
326       •   PDL::CallExt
327
328           Allows you to call functions using external shared libraries.  This
329           is an alternative to using PDL::PP.  The major difference between
330           PDL::PP and PDL::CallExt is that the former will handle threading
331           over implicit thread dimensions for you, whereas PDL::CallExt
332           simply calls an external function.  PDL::PP is generally the
333           recommended way to interface your code with PDL, but it wouldn't be
334           Perl if there wasn't another way to do it.
335
336       •   PDL::Config
337
338           Defines the %PDL::Config hash, which has lots of useful information
339           pertinent to your PDL build.
340
341       •   PDL::Doc
342
343           Explanation of the PDL documentation conventions, and an interface
344           to the PDL Documentation parser.  Following these guidelines when
345           writing documentation for PDL functions will ensure that your
346           wonderful documentation is accessible from the perldl shell and
347           from calls to "barf".  (Did you notice that "barf" used your
348           documentation?  Time to reread PDL::Core...)
349
350       •   PDL::Exporter
351
352           A simple replacement for the standard Exporter module.  The only
353           major difference is that the default imported modules are those
354           marked ':Func'.
355
356       •   PDL::Types
357
358           Defines some useful functions for getting an ndarray's type, as
359           well as getting information about that type.
360

Expert Usage

362       •   PDL::Core::Dev
363
364           Provides some decently useful functions that are pretty much only
365           needed by the PDL Porters.
366
367       •   PDL::API
368
369           Explains how to make an ndarray by hand, from Perl or your C source
370           code, using the PDL API.
371
372       •   PDL::Internals
373
374           Explains the nitty-gritty of the PDL data structures.  After
375           reading this (a few times :), you should be able to create an
376           ndarray completely from scratch (i.e. without using the PDL API).
377           Put a little differently, if you want to understand how PDL::PP
378           works, you'll need to read this.
379
381       Copyright 2010 David Mertens (dcmertens.perl@gmail.com). You can
382       distribute and/or modify this document under the same terms as the
383       current Perl license.
384
385       See: http://dev.perl.org/licenses/
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389perl v5.34.0                      2021-08-16                         COURSE(1)
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