NAME

Finance::Shares::rate_of_change - Calculate how fast a line is changing

SYNOPSIS

Two examples of how to specify a rate of change line, one showing the minimum required and the other illustrating all the possible fields.

    use Finance::Shares::Model;
    use Finance::Shares::rate_of_change;

    my @spec = (
	...
	lines => [
	    ...
	    minimal => {
		function => 'rate_of_change',
	    },
	    full = {
		function => 'rate_of_change',
		graph    => 'Stock Prices',
		gtype    => 'price',
		line     => 'some_line',
		period   => 10,
		key      => '10 day rate of change',
		style    => { ... },
		shown    => 1,
		order    => -99,
	    },
	    ...
	],
	...
	samples => [
	    ...
	    one => {
		lines => ['full', 'minimal'],
		...
	    }
	],
    );

    my $fsm = new Finance::Shares::Model( @spec );
    $fsm->build();

DESCRIPTION

The rate of change is calulcated using values taken now and N periods in the past. A ratio of current/old values is adjusted to give values centered around zero. So a 5 weekday rate of change of closing price would show how much higher (or lower) todays close was compared to this time last week.

When period is 1, the rate_of_change line is a resonable approximation to the rate of change of the source.

The results are normally displayed on an 'analysis' graph as the changes may be positive or negative values. WARNING: if you specify a graph for the momentum line, it will NOT relate to the Y axis. '0' will probably be around the middle (vertically) of the momentum line, while for the Y axis, '0' may well be below the bottom of the page.

To get the line to appear, there must be an entry within the lines block of a Finance::Shares::Model specification. This hash ref must have a function field with the value momentum. The entry's tag must then appear in the line field of a sample.

The other main fields are line and period.

OPTIONS

function

Required. Must be rate_of_change.

graph

If present, this should be a tag declared as a charts resource. It identifies a particular graph within a chart page. A gtype is implied. (No default)

gtype

Required, unless graph is given. This specifies the type of graph the function lines should appear on. It should be one of price, volume, analysis or level. (Default: price)

line

Identifies the line whose data is to be considered. (Default: 'close')

period

The number of values to use. The actual time will depend on the dates by field. (Default: 5)

Normally at least this number of dates will have been read in before the first date shown on the chart. However, a small initial gap may be visible if some of that working data was missing. Set the dates before field to adjust this.

key

Most functions generate suitable (if lengthy) entries. This provides the opportunity to identify the line in the Key panel, next to the style.

order

The entries on the graph are sorted according to this value, which defaults to the order required for calculation. A large integer will bring the line to the front and a negative number will put it behind all the rest.

Examples

-1

The line goes behind the data.

0.5

In front of the data, but only just.

999

Probably the top line.

shown

1 for the line to be shown, 0 hides it. (Default: 1)

style

This is normally a hash ref defining the data's appearance. See PostScript::Graph::Style for full details, or "Lines" in Finance::Shares::Model for an example.

BUGS

Please let me know when you suspect something isn't right. A short script working from a CSV file demonstrating the problem would be very helpful.

AUTHOR

Chris Willmot, chris@willmot.org.uk

LICENCE

Copyright (c) 2002-2003 Christopher P Willmot

This program is free software; you can redistribute it and/or modify it under the terms of the GNU General Public License as published by the Free Software Foundation; either version 2 of the License, or (at your option) any later version.

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. See the GNU General Public License for more details. A copy can be found at http://www.gnu.org/copyleft/gpl.html

SEE ALSO

Finance::Shares::Overview provides an introduction to the suite, and fsmodel is the principal script.

Modules involved in processing the model include Finance::Shares::Model, Finance::Shares::MySQL, Finance::Shares::Chart. Chart and file details may be found in PostScript::File, PostScript::Graph::Paper, PostScript::Graph::Key, PostScript::Graph::Style.

All functions are invoked from their own modules, all with lower-case names such as Finance::Shares::moving_average. The nitty-gritty on how to write each line specification are found there.

The quote data is stored in a Finance::Shares::data object. For information on writing additional line functions see Finance::Share::Function and Finance::Share::Line. Also, Finance::Share::test covers writing your own tests.

cpanm Finance::Shares::Line

perl -MCPAN -e shell
install Finance::Shares::Line