Spreadsheet::Engine::Function::VAR - Spreadsheet funtion VAR()

Spreadsheet-Engine documentation Contained in the Spreadsheet-Engine distribution.

Index

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NAME

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Spreadsheet::Engine::Function::VAR - Spreadsheet funtion VAR()

SYNOPSIS

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  =VAR(list_of_numbers)

DESCRIPTION

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This returns the variance.

We calculate as per Knuth "The Art of Computer Programming" Vol. 2 3rd edition, page 232

HISTORY

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This is a Modified Version of code extracted from SocialCalc::Functions in SocialCalc 1.1.0

COPYRIGHT

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Portions (c) Copyright 2005, 2006, 2007 Software Garden, Inc. All Rights Reserved.

Portions (c) Copyright 2007 Socialtext, Inc. All Rights Reserved.

Portions (c) Copyright 2007, 2008 Tony Bowden

LICENCE

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The contents of this file are subject to the Artistic License 2.0; you may not use this file except in compliance with the License. You may obtain a copy of the License at http://www.perlfoundation.org/artistic_license_2_0

Spreadsheet-Engine documentation Contained in the Spreadsheet-Engine distribution. 
package Spreadsheet::Engine::Function::VAR;

use strict;
use warnings;

use base 'Spreadsheet::Engine::Fn::series';

sub calculate {
  return sub {
    my ($in, $A) = @_;
    return $A = { mk1 => $in->value, sk1 => 0, count => 1 }
      unless defined $A;

    my $diff = $in->value - $A->{mk1};
    $A->{mk}  = $A->{mk1} + $diff / ++$A->{count};
    $A->{sk}  = $A->{sk1} + $diff * ($in->value - $A->{mk});
    $A->{sk1} = $A->{sk};
    $A->{mk1} = $A->{mk};
    return $A;
  };
}

sub result_from {
  my ($self, $A) = @_;
  die Spreadsheet::Engine::Error->div0 unless $A->{count} > 1;
  return $A->{sk} / ($A->{count} - 1);
}

1;

__END__