pdl::reduce(3) [suse man page]
Reduce(3) User Contributed Perl Documentation Reduce(3) 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 v5.12.1 2009-10-17 Reduce(3)
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Matrix(3pm) User Contributed Perl Documentation Matrix(3pm) NAME
PDL::Matrix -- a convenience matrix class for column-major access VERSION
This document refers to version PDL::Matrix 0.5 of PDL::Matrix SYNOPSIS
use PDL::Matrix; $m = mpdl [[1,2,3],[4,5,6]]; $m = PDL::Matrix->pdl([[1,2,3],[4,5,6]]); $m = msequence(4,3); @dimsa = $a->mdims; # 'dims' is not overloaded $v = vpdl [0,1,2,3] $v = vzeroes(4); DESCRIPTION
Overview This package tries to help people who want to use PDL for 2D matrix computation with lots of indexing involved. It provides a PDL subclass so one- and two-dimensional piddles that are used as vectors resp and matrices can be typed in using traditional matrix convention. If you want to know more about matrix operation support in PDL, you want to read PDL::MatrixOps or PDL::Slatec. The original pdl class refers to the first index as the first row, the second index as the first column of a matrix. Consider print $B = sequence(3,2) [ [0 1 2] [3 4 5] ] which gives a 2x3 matrix in terms of the matrix convention, but the constructor used (3,2). This might get more confusing when using slices like sequence(3,2)->slice("1:2,(0)") : with traditional matrix convention one would expect [2 4] instead of [1 2]. This subclass PDL::Matrix overloads the constructors and indexing functions of pdls so that they are compatible with the usual matrix convention, where the first dimension refers to the row of a matrix. So now, the above example would be written as print $B = PDL::Matrix->sequence(3,2) # or $B = msequence(3,2) [ [0 1] [2 3] [4 5] ] Routines like eigens or inv can be used without any changes. Furthermore one can construct and use vectors as n x 1 matrices without mentioning the second index '1'. Implementation "PDL::Matrix" works by overloading a number of PDL constructors and methods such that first and second args (corresponding to first and second dims of corresponding matrices) are effectively swapped. It is not yet clear if PDL::Matrix achieves a consistent column-major look-and-feel in this way. NOTES
As of version 0.5 (rewrite by CED) the matrices are stored in the usual way, just constructed and stringified differently. That way indexing and everything else works the way you think it should. FUNCTIONS
mpdl, PDL::Matrix::pdl constructs an object of class PDL::Matrix which is a piddle child class. $m = mpdl [[1,2,3],[4,5,6]]; $m = PDL::Matrix->pdl([[1,2,3],[4,5,6]]); mzeroes, mones, msequence constructs a PDL::Matrix object similar to the piddle constructors zeroes, ones, sequence. vpdl constructs an object of class PDL::Matrix which is of matrix dimensions (n x 1) print $v = vpdl [0,1]; [ [0] [1] ] vzeroes, vones, vsequence constructs a PDL::Matrix object with matrix dimensions (n x 1), therefore only the first scalar argument is used. print $v = vsequence(2); [ [0] [1] ] kroneckerproduct returns kroneckerproduct of two matrices. This is not efficiently implemented. det_general returns a generalized determinant of a matrix. If the matrix is not regular, one can specify the rank of the matrix and the corresponding subdeterminant is returned. This is implemented using the "eigens" function. trace returns the trace of a matrix (sum of diagonals) BUGS AND PROBLEMS
Because we change the way piddles are constructed, not all pdl operators may be applied to piddle-matrices. The inner product is not redefined. We might have missed some functions/methods. Internal consistency of our approach needs yet to be established. Because PDL::Matrix changes the way slicing behaves, it breaks many operators, notably those in MatrixOps. TODO
check all PDL functions, benchmarks, optimization, lots of other things ... AUTHOR(S) Stephan Heuel (stephan@heuel.org), Christian Soeller (c.soeller@auckland.ac.nz). COPYRIGHT
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 Matrix(3pm)