PDL::Reduce -- a reduce
function for PDL
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).
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
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.
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
.
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.