=head1 NAME

PDL::Intro - Introduction to the Perl Data Language

Version 2.4

"Why is it that we entertain the belief that for every purpose odd
numbers are the most effectual?" - Pliny the Elder.

I<Karl Glazebrook [karlglazebrook@yahoo.com]> and 
I<Craig DeForest  [deforest@boulder.swri.edu>

=head1 DESCRIPTION

Perl Data Language (PDL) is a perl extension that is designed for scientific
and bulk numeric data processing and display.  It extends perl's syntax and
includes fully vectorized, multidimensional array handling, plus several 
paths for device-independent graphics output. 

C<pdl> is an interactive command shell that is supplied with PDL; for
more information, see L<perldl(1)|perldl>.

Because PDL is a modular extension to perl, it is accessible to
ordinary perl scripts: to write a command-line PDL script you just say
"use PDL;" at the top of an ordinary perl script.  There is also a
specialized interactive shell (L<perldl(1)|perldl>) that allows you to
issue PDL commands interactively and that includes a path-based
subroutine autoloader similar to those found in MatLab and IDL (which
are trademarks of MathWorks and Kodak, respectively).  The perldl
shell allows you to quickly manipulate and "play with" your data.  (You
can also invoke it with the shorter command "pdl").

The C<PDL> module is a complete Object-Oriented extension to Perl
(although you don't have to know what an object is to use it) which
allows large N-dimensional data sets, such as large images, spectra,
time series, etc to be stored B<efficiently> and manipulated B<en
masse>.  For example with the PDL module we can write the perl code
C<$a=$b+$c>, where C<$b> and C<$c> are large datasets (e.g. 2048x2048
images), and get the result in only a fraction of a second.

PDL variables (or I<piddles> as they have come to be known)
support a wide range of fundamental data types - arrays can be bytes,
short integers (signed or unsigned), long integers, floats or
double precision floats. And because of the Object-Oriented nature
of PDL new customised datatypes can be derived from them.

Perl is an extremely good and versatile scripting language, well
suited to beginners, and allows rapid prototyping.  The PDL extensions
to the language use Perl's object-oriented capabilities to seamlessly
add high-speed scientific capabilities that are themselves written in
perl, C and/or FORTRAN as appropriate -- so your code's "hot spots"
run at native compiled-language speed, while you work in the higher
level perl language (which itself runs faster than many other
JIT-compiled or interpreted languages).

External modules that have been incorporated into PDL include the
complete Gnu Scientific Library; CFITSIO for FITS file handling; FFTW;
the Slatec matrix-handling package; and the PGPLOT, PLPLOT, Karma, and
OpenGL graphics libraries.  Ancillary packages written in PDL itself
include image handling, curve fitting, matrix manipulation, coordinate
transformation, nonlinear data resampling, graphics I/O, and extensive
file I/O utilities.  Because PDL programs are "just" perl with
additional modules loaded, the entire CPAN archive is also available
to your PDL scripts.

=head1 SYNOPSIS

This manual page provides a general introduction to the underlying
philosophy of PDL. For an overview over the rest of the documentation
see L<PDL::Index|PDL::Index>. As a beginner the following
documents are particulary recommended:

=over 4

=item L<PDL::Impatient>

Quick summary - PDL for the impatient

=item L<PDL::FAQ>

The Frequently Asked Questions list for PDL.

=item L<PDL::Philosophy>

Why another matrix language?

=item L<PDL::Indexing>

An introduction to using smart indices in PDL.

=item L<PDL::NiceSlice>

The all important I<slicing> of piddles.

=back

=head1 AUTHOR

Copyright (C) Karl Glazebrook (karlglazebrook@yahoo.com), Tuomas J. Lukka,
(lukka@husc.harvard.edu) and Christian Soeller (c.soeller@auckland.ac.nz)
1997-2002.

Commercial reproduction of this documentation in a different format
is forbidden without permission.

=cut