/ 
Text-NumericData-2.003003
River stage zero No dependents
/ Text::NumericData::FileCalc

NAME

Text::NumericData::FileCalc - calculations on data sets with optional support from auxilliary data files

SYNOPSIS

Simple:

use Text::NumericData::Calc qw(formula_function);
use Text::NumericData::FileCalc qw(file_calc);

@data = ([0], [30], [90]);
$ff = formula_function('[2]=sin([1]/180*pi)');
# result: @data = ([0,0], [30,0.5], [90,1])

Elaborate with context:

use Text::NumericData::Calc qw(formula_function);
use Text::NumericData::File;
use Text::NumericData::FileCalc qw(file_calc);

@data = ([1, 2, 3],[4, 5, 6]);
@aux = (Text::NumericData::File->new({}, '/some/file.txd'));
@A = ();
@C = (42);
# Defaults.
%config = (bycol=>0, interpolate=>1, byrow=>0);
# Prepare function.
$ff = formula_function('[2]*=[1,2] + C0; A0+=[2]');
# Evaluate on @data.
$deletelist = file_calc($ff, \@data, \@aux, \@A, \@C, \%config);
# On error, deletelist is undefined.

DESCRIPTION

A possibly elaborate computation involving extra Text::NumericData file handles to use data from and optional read/write data in @A and constants in @C. The configuration hash is about choosing whether to correlate data via the row index or via values in a certain column (the first one by default); in the latter case also if to use interpolation (on by default).

The elaborate example above will add to column 2 the value of column 2 in the first extra file ($txdb) multiplied by 42. Also, A0 will contain the sum over this new column 2. The configuration hash can influence things:

# do not use interpolation
$config{interpolation} = 0;
# correlate via 3rd column (beware of 0-based index here)
$config{bycol} = 2;
# even more elaborate:
# Use col 2 in main file, but correlate to respective value
# in col 6 of first extra file, col 3 of the second.
$config{fromcol} = [6,3];
# changed my mind, correlate simply via row index
$config{byrow} = 1;

Data sets that can not be correlated to the extra files will be marked for deletion (the zero-based index returned in an array reference). Also, you can return a true value from your formula to indicate that a data set should be deleted:

# Filter stuff outside our range.
file_calc('return 1 if ([1] < 0.3 or [1] > 0.7)');

I know, this sounds a bit backwards, but it makes sense considering the general law of lazyness causing the normal case to return nothing, meaning 'false'. Also, please stick to 1 as numerical value... I might consider adding some whistles based on exact return value in future.

For formula syntax, see Text::NumericData::Calc.

AUTHOR

Thomas Orgis <thomas@orgis.org>

COPYRIGHT AND LICENSE

Copyright (C) 2004-2013, Thomas Orgis.

This module is free software; you can redistribute it and/or modify it under the same terms as Perl 5.10.0. For more details, see the full text of the licenses in the directory LICENSES.

This program is distributed in the hope that it will be useful, but without any warranty; without even the implied warranty of merchantability or fitness for a particular purpose.