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);

[ 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

]

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 [,$dim]);

reduce applies the named operation along the specified dimension reducing the input piddle dimension by one. If the dimension is omitted the operation is applied along the first dimension. To get a list of valid operations see canreduce.

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.