Just type help (shortcut = ''?'') at the perldl prompt and proceed from there. Another useful command is the apropos (shortcut = ''??'') command. Ok, you are right in a way. The docs say that pdls can be thought of arrays. More specifically, it says ( PDL::Impatient ): I find when using perlDL it is most useful to think of standard perl @x variables as "lists" of generic "things" and PDL variables like $x as "arrays" which can be contained in lists or hashes.

If you have a certain project in mind you should check if somebody else is already working on it or if you could benefit from existing modules. Do so by posting your planned project to the PDL developers mailing list at pdl-porters@jach.hawaii.edu . To subscribe, send a message to pdl-porters-request@jach.hawaii.edu containing a string in the following format: where you should replace the string me@my.email.address with your email address.

PDL stands for Perl Data Language . To say it with the words of Karl Glazebrook, initiator of the PDL project: The PDL concept is to give standard perl5 the ability to COMPACTLY store and SPEEDILY manipulate the large N-dimensional data sets which are the bread and butter of scientific computing. e.g. $a=$b+$c can add two 2048x2048 images in only a fraction of a second.

The complete PDL documentation is available with the PDL distribution. If you have PDL installed on your machine and are on a unix like system then you can read the PDL manuals with the man command. man PDL::Intro will lead the way to other PDL manual pages. In any case (i.e. also on non-unixes) perldoc PDL::Intro should work. The easiest way by far, however, to get familiar with PDL is to use the PDL online help facility from within the perldl shell. Just type perldl at your system prompt.

Yes, as of December 1999, PDL is available at the CVS repository on http://www.sourceforge.net . The tree is updated by developers who have accounts on Sourceforge and snapshots of the tree are released regularly by the pumpkin holder (the pumpking).

null is a special token for 'empty piddle'. A null pdl can be used to flag to a PDL function that it should create an appropriately sized and typed piddle. Null piddles can be used in places where a PDL function expects an output or temporary argument. Output and temporary arguments are flagged in the signature of a PDL function with the [o] and [t] qualifiers (see next question if you don't know what the signature of a PDL function is).

Questions like this should be a thing of the past with the PDL online help system in place. Just try (after installation):

We are delighted to be able to give you the nicest possible answer on a question like this: PDL is *free software* and all sources are publicly available. But still, there are some copyrights to comply with. So please, try to be as nice as we (the PDL authors) are and try to comply with them. Oh, before you think it is *completely* free: you have to invest some time to pull the distribution from the net, compile and install it and (maybe) read the manuals.

This is version 0.6 of the PDL FAQ, a collection of frequently asked questions about PDL - the Perl Data Language. You can find the latest version of this document at http://pdl.perl.org/faq.html . This FAQ will be monthly posted to the PDL mailing list perldl@jach.hawaii.edu . This is a considerably reworked version of the PDL FAQ. As such many errors might have crept in and many updates might not have made it in.

PDL is supported by its users. General informal support for PDL is provided through the PDL mailing list ( perldl@jach.hawaii.edu , see below). a Perl extension (see below) it is devoted to the idea of free and open development put forth by the Perl community. PDL was and is being actively developed by a loosely knit group of people around the world who coordinate their activities through the PDL development mailing list ( pdl-porters@jach.hawaii.edu , see below).

PDL is a Perl5 extension package. As such it needs an existing Perl5 installation (see below) to run. Furthermore, much of PDL is written in perl (+ some core functionality that is written in C). PDL programs are (syntactically) just perl scripts that happen to use some of the functionality implemented by the package '' PDL '' ;

Since PDL is just a Perl package you need first of all an installation of Perl on your machine. As of this writing PDL requires version 5.004 of Perl, version 5.004_4 or higher is strongly recommended. More information on where and how to get a Perl installation can be found at the Perl home page http://www.perl.com and at many CPAN sites (if you do not know what CPAN is check the answer to the next question).

First of all, for all purely Perl-related questions there are tons of sources on the net. A good point to start is http://www.perl.com . The PDL home site can be accessed by pointing your web browser to http://pdl.perl.org . It has tons of goodies for anyone interested in PDL: Name of the current pumpkin holders for the different PDL modules (if you want to know what that means you better had a look at the web pages). Thanks to the efforts of Frossie ( frossie@jach.hawaii.

of this writing (FAQ version 0.6 of 01/06/2000 ) the latest released version is 2.006 . The latest versions should always be available from a CPAN mirror site near you (see above for info on where to get PDL). The most current version of PDL can be obtained from the CVS repository see ''CVS availability of PDL'' below.

Unfortunately, in the context of PDL the term threading can have two different (but related) meanings: When mentioned in the INSTALL directions and possible during the build process we have the usual computer science meaning of multithreading in mind (useful mainly on multiprocessor machines or clusters) PDL threading of operations on piddles (as mentioned in the indexing docs) is the iteration of a basic operation over appropriate subslices of piddles, e.g.

The signature of a function is an important concept in PDL. Many (but not all) PDL function have a signature which specifies the arguments and their (minimal) dimensionality. As an example, look at the signature of the maximum function: this says that maximum takes two arguments, the first of which is (at least) one-dimensional while the second one is zero-dimensional and an output argument (flagged by the [o] qualifier).

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