Perl Data Language (abbreviated PDL) is a set of
free software
Free software or libre software is computer software distributed under terms that allow users to run the software for any purpose as well as to study, change, and distribute it and any adapted versions. Free software is a matter of liberty, n ...
array programming extensions to the
Perl programming language. PDL extends the data structures built into Perl, to include large
multidimensional arrays, and adds functionality to manipulate those arrays as vector objects. It also provides tools for
image processing,
machine learning
Machine learning (ML) is a field of inquiry devoted to understanding and building methods that 'learn', that is, methods that leverage data to improve performance on some set of tasks. It is seen as a part of artificial intelligence.
Machine ...
,
computer modeling of physical systems, and graphical plotting and presentation. Simple operations are automatically vectorized across complete arrays, and higher-dimensional operations (such as matrix multiplication) are supported.
Language design
PDL is a vectorized
array programming
In computer science, array programming refers to solutions which allow the application of operations to an entire set of values at once. Such solutions are commonly used in scientific and engineering settings.
Modern programming languages that ...
language: the expression syntax is a variation on standard mathematical
vector notation, so that the user can combine and operate on large arrays with simple expressions. In this respect, PDL follows in the footsteps of the
APL programming language, and it has been compared to commercial languages such as
MATLAB
MATLAB (an abbreviation of "MATrix LABoratory") is a proprietary multi-paradigm programming language and numeric computing environment developed by MathWorks. MATLAB allows matrix manipulations, plotting of functions and data, implementat ...
and
Interactive Data Language, and to other free languages such as
NumPy and
Octave. Unlike MATLAB and IDL, PDL allows great flexibility in indexing and vectorization: for example, if a subroutine normally operates on a 2-D
matrix
Matrix most commonly refers to:
* ''The Matrix'' (franchise), an American media franchise
** '' The Matrix'', a 1999 science-fiction action film
** "The Matrix", a fictional setting, a virtual reality environment, within ''The Matrix'' (franchi ...
array, passing it a 3-D
data cube will generally cause the same operation to happen to each 2-D layer of the cube.
PDL borrows from Perl at least three basic types of program structure:
imperative programming,
functional programming
In computer science, functional programming is a programming paradigm where programs are constructed by applying and composing functions. It is a declarative programming paradigm in which function definitions are trees of expressions tha ...
, and
pipeline programming forms may be combined. Subroutines may be loaded either via a built-in
autoload
In computer programming, autoloading is the capability of loading and linking portions of a program from mass storage automatically when needed, so that the programmer is not required to define or include those portions of the program explicitl ...
mechanism or via the usual Perl module mechanism. In 2000, it was proposed that PDL-like functionality be included in the development of what is now
Raku.
Graphics
True to the
glue language roots of Perl, PDL borrows from several different modules for graphics and plotting support.
NetPBM provides image file I/O (though FITS is supported natively).
Gnuplot
gnuplot is a command-line and GUI program that can generate two- and three-dimensional plots of functions, data, and data fits. The program runs on all major computers and operating systems (Linux, Unix, Microsoft Windows, macOS, FreeDOS, ...
,
PLplot,
PGPLOT, and
Prima modules are supported for 2-D graphics and plotting applications, and
Gnuplot
gnuplot is a command-line and GUI program that can generate two- and three-dimensional plots of functions, data, and data fits. The program runs on all major computers and operating systems (Linux, Unix, Microsoft Windows, macOS, FreeDOS, ...
and
OpenGL are supported for 3-D plotting and rendering.
I/O
PDL provides facilities to read and write many open data formats, including
JPEG,
PNG,
GIF,
PPM,
MPEG,
FITS,
NetCDF,
GRIB, raw binary files, and delimited ASCII tables. PDL programmers can use the
CPAN
The Comprehensive Perl Archive Network (CPAN) is a repository of over 250,000 software modules and accompanying documentation for 39,000 distributions, written in the Perl programming language by over 12,000 contributors. ''CPAN'' can denote ei ...
Perl I/O libraries to read and write data in hundreds of standard and niche file formats.
Machine learning
PDL can be used for
machine learning
Machine learning (ML) is a field of inquiry devoted to understanding and building methods that 'learn', that is, methods that leverage data to improve performance on some set of tasks. It is seen as a part of artificial intelligence.
Machine ...
. It includes modules that are used to perform classic
k-means clustering or general and generalized linear modeling methods such as ANOVA, linear regression, PCA, and logistic regression. Examples of PDL usage for regression modelling tasks include evaluating association between education attainment and ancestry differences of parents,
comparison of RNA-protein interaction profiles that needs regression-based normalization
and analysis of spectra of galaxies.
perldl
An installation of PDL usually comes with an interactive
shell known as perldl, which can be used to perform simple calculations without requiring the user to create a Perl program file. A typical session of perldl would look something like the following:
perldl> $x = pdl 1, 2 One-two, 1-2, 1 & 2 or 1+2 may refer to:
Sports
* Push and run, in association football
* One-two combo, in boxing
Music
* '' One, Two'', album by Sister Nancy
* ''1 + 2'' (album), album by Recoil
* ''Volumes 1 & 2'' (The Desert Sessions album ...
, 4
The comma is a punctuation mark that appears in several variants in different languages. It has the same shape as an apostrophe or single closing quotation mark () in many typefaces, but it differs from them in being placed on the baseline o ...
;
perldl> $y = pdl 5, 6, 7, 9, 0
The comma is a punctuation mark that appears in several variants in different languages. It has the same shape as an apostrophe or single closing quotation mark () in many typefaces, but it differs from them in being placed on the baseline o ...
;
perldl> $z = $x x $y;
perldl> p $z;
_[21_24__7_[47_54_21.html"_;"title="1_24__7.html"_;"title="_[21_24__7">_[21_24__7_[47_54_21">1_24__7.html"_;"title="_[21_24__7">_[21_24__7_[47_54_21.html" ;"title="1_24__7">_[21_24__7_[47_54_21.html" ;"title="1_24__7.html" ;"title=" [21 24 7"> [21 24 7 [47 54 21">1_24__7.html" ;"title=" [21 24 7"> [21 24 7 [47 54 21">1_24__7">_[21_24__7_[47_54_21.html" ;"title="1_24__7.html" ;"title=" [21 24 7"> [21 24 7 [47 54 21">1_24__7.html" ;"title=" [21 24 7"> [21 24 7 [47 54 21
The commands used in the shell are Perl statements that can be used in a program with
PDL
module included.
x
is an overloaded operator for matrix multiplication, and
p
in the last command is a shortcut for
print
.
Implementation
The core of PDL is written in C (programming language), C. Most of the functionality is written in PP, a PDL-specific metalanguage that handles the vectorization of simple C snippets and interfaces them with the Perl host language via Perl's
XS (Perl), XS compiler. Some modules are written in
Fortran, with a C/PP interface layer. Many of the supplied functions are written in PDL itself. PP is available to the user to write C-language extensions to PDL. There is also an Inline module (Inline::Pdlpp) that allows PP function definitions to be inserted directly into a Perl script; the relevant code is low-level compiled and made available as a Perl subroutine.
The PDL API uses the basic Perl 5 object-oriented functionality: PDL defines a new type of Perl scalar object (
eponym
An eponym is a person, a place, or a thing after whom or which someone or something is, or is believed to be, named. The adjectives which are derived from the word eponym include ''eponymous'' and ''eponymic''.
Usage of the word
The term ''epon ...
ously called a "PDL", or "ndarray") that acts as a Perl scalar, but that contains a conventional
typed array of numeric or character values. All of the standard Perl operators are overloaded so that they can be used on PDL objects transparently, and PDLs can be mixed-and-matched with normal Perl scalars. Several hundred object methods for operating on PDLs are supplied by the core modules.
Raku version
In
Raku, PDL is specified as a trait in Synopsis 9.
[ ] As of January 2013, this feature is not yet implemented in
Rakudo.
See also
*
Comparison of numerical-analysis software
*
List of numerical-analysis software
Listed here are notable end-user computer applications intended for use with numerical or data analysis:
Numerical-software packages
General-purpose computer algebra systems
Interface-oriented
Language-oriented
Historically signific ...
References
External links
* {{Official website, http://pdl.perl.org/
PDL Quick ReferencePDL Intro & resources
Tutorial lecture on PDLDraft release of the PDL Book for PDL-2.006Example of PDL usage in the scientific literature
Array programming languages
Free mathematics software
Free science software
Numerical programming languages
Perl modules