pdl::reduce(3pm) [debian man page]

Reduce(3pm)						User Contributed Perl Documentation					       Reduce(3pm)

NAME

       PDL::Reduce -- a "reduce" function for PDL

DESCRIPTION

       Many languages have a "reduce" function used to reduce the rank of an N-D array by one. It works by applying a selected operation along a
       specified dimension. This module implements such a function for PDL by providing a simplified interface to the existing projection
       functions (e.g. "sumover", "maximum", "average", etc).

SYNOPSIS

	use PDL::Reduce;
	$a = sequence 5,5;
	# reduce by adding all
	# elements along 2nd dimension
	$b = $a->reduce('add',1);
	@ops = $a->canreduce; # return a list of all allowed operations

FUNCTIONS

   reduce
       reduce dimension of piddle by one by applying an operation along the specified dimension

	$a = sequence 5,5;
	# reduce by adding all
	# elements along 2nd dimension
	$b = $a->reduce('add',1);
	$b = $a->reduce('plus',1);
	$b = $a->reduce('+',1);     # three ways to do the same thing

       [ As an aside: if you are familiar with threading you will see that this is actually the same as

	$b = $a->mv(1,0)->sumover

       ]

       NOTE: You should quote the name of the operation (1st arg) that you want "reduce" to perform. This is important since some of the names are
       identical to the names of the actual PDL functions which might be imported into your namespace. And you definitely want a string as
       argument, not a function invocation! For example, this will probably fail:

	 $b = $a->reduce(avg,1); # gives an error from invocation of 'avg'

       Rather use

	 $b = $a->reduce('avg',1);

       "reduce" provides a simple and unified interface to the projection functions and makes people coming from other data/array languages
       hopefully feel more at home.

	$result = $pdl->reduce($operation [,@dims]);

       "reduce" applies the named operation along the specified dimension(s) reducing the input piddle dimension by as many dimensions as supplied
       as arguments. If the dimension(s) argument is omitted the operation is applied along the first dimension. To get a list of valid operations
       see canreduce.

       NOTE - new power user feature: you can now supply a code reference as operation to reduce with.

	 # reduce by summing over dims 0 and 2
	 $result = $pdl->reduce(&sumover, 0, 2);

       It is your responsibility to ensure that this is indeed a PDL projection operation that turns vectors into scalars!  You have been warned.

   canreduce
       return list of valid named "reduce" operations Some common operations can be accessed using a number of names, e.g. '+', "add" and "plus"
       all sum the elements along the chosen dimension.

	 @ops = PDL->canreduce;

       This list is useful if you want to make sure which operations can be used with "reduce".

AUTHOR

       Copyright (C) 2000 Christian Soeller (c.soeller@auckland.ac.nz). All rights reserved. There is no warranty. You are allowed to redistribute
       this software / documentation under certain conditions. For details, see the file COPYING in the PDL distribution. If this file is
       separated from the PDL distribution, the copyright notice should be included in the file.

perl v5.14.2							    2011-03-30							       Reduce(3pm)

Dbg(3pm)						User Contributed Perl Documentation						  Dbg(3pm)

NAME

       PDL::Dbg - functions to support debugging of PDL scripts

SYNOPSIS

	      use PDL;
	      use PDL::Dbg;

	      $c = $a->slice("5:10,2:30")->px->diagonal(3,4);
	      PDL->px;

DESCRIPTION

       This packages implements a couple of functions that should come in handy when debugging your PDL scripts. They make a lot of sense while
       you're doing rapid prototyping of new PDL code, let's say inside the perldl or pdl2 shell.

FUNCTIONS

   px
       Print info about a piddle (or all known piddles)

	   pdl> PDL->px
	   pdl> $b += $a->clump(2)->px('clumptest')->sumover
	   pdl> $a->px('%C (%A) Type: %T') # prints nothing unless $PDL::debug
	   pdl> $PDL::debug = 1
	   pdl>  $a->px('%C (%A) Type: %T')
	   PDL(52433464) Type: Double

       This function prints some information about piddles. It can be invoked as a class method (e.g. "PDL->px" ) or as an instance method (e.g.
       "$pdl->px($arg)"). If

       invoked as a class method
	 it prints info about all piddles found in the current package (excluding "my" variables). This comes in quite handy when you are not
	 quite sure which pdls you have already defined, what data they hold , etc. "px" is supposed to support inheritance and prints info about
	 all symbols for which an "isa($class)" is true. An optional string argument is interpreted as the package name for which to print
	 symbols:

	   pdl> PDL->px('PDL::Mypack')

	 The default package is that of the caller.

       invoked as an instance method
	 it prints info about that particular piddle if $PDL::debug is true and returns the pdl object upon completion. It accepts an optional
	 string argument that is simply prepended to the default info if it doesn't contain a "%" character. If, however, the argument contains a
	 "%" then the string is passed to the "info" method to control the format of the printed information. This can be used to achieve
	 customized output from "px". See the documentation of "PDL::info" for further details.

       The output of px will be determined by the default formatting string that is passed to the "info" method (unless you pass a string
       containing "%" to px when invoking as an instance method, see above). This default string is stored in $PDL::Dbg::Infostr and the default
       output format can be accordingly changed by setting this variable.  If you do this you should also change the default title string that the
       class method branch prints at the top of the listing to match your new format string. The default title is stored in the variable
       $PDL::Dbg::Title.

       For historical reasons "vars" is an alias for "px".

   vars
       Alias for "px"

BUGS

       There are probably some. Please report if you find any. Bug reports should be sent to the PDL mailing list perldl@jachw.hawaii.edu.

AUTHOR

       Copyright(C) 1997 Christian Soeller (c.soeller@auckland.ac.nz).	All rights reserved. There is no warranty. You are allowed to redistribute
       this software / documentation under certain conditions. For details, see the file COPYING in the PDL distribution. If this file is
       separated from the PDL distribution, the copyright notice should be included in the file.

perl v5.14.2							    2012-01-02								  Dbg(3pm)