93 lines
2.0 KiB
Perl
93 lines
2.0 KiB
Perl
# -*- perl -*-
|
|
package Smokeping::RRDhelpers;
|
|
|
|
=head1 NAME
|
|
|
|
Smokeping::RRDhelpers - Functions for doing 'interesting things' with RRDs.
|
|
|
|
=head1 OVERVIEW
|
|
|
|
This module holds a collection of functions for doing advanced calculations
|
|
and effects on rrd files.
|
|
|
|
=cut
|
|
|
|
use strict;
|
|
use RRDs;
|
|
|
|
=head2 IMPLEMENTATION
|
|
|
|
=head3 get_stddev(rrd,ds,cf,start,end[,step])
|
|
|
|
Pull the data values off the rrd file and calculate the standard deviation. Nan
|
|
values get ignored in this process.
|
|
|
|
=cut
|
|
|
|
sub get_stddev{
|
|
my $rrd = shift;
|
|
my $ds = shift;
|
|
my $cf = shift;
|
|
my $start = shift;
|
|
my $end = shift;
|
|
my $step = shift;
|
|
my ($realstart,$realstep,$names,$array) = RRDs::fetch $rrd, $cf, '--start',$start, '--end',$end,($step ? ('--resolution',$step):());
|
|
if (my $err = RRDs::error){
|
|
warn $err
|
|
};
|
|
my $idx = 0;
|
|
for (@$names){
|
|
last if $ds eq $_;
|
|
$idx ++;
|
|
}
|
|
my $sum = 0;
|
|
my $sqsum = 0;
|
|
my $cnt = 0;
|
|
foreach my $line (@$array){
|
|
my $val = $line->[$idx];
|
|
if (defined $val){
|
|
$cnt++;
|
|
$sum += $val;
|
|
$sqsum += $val**2;
|
|
}
|
|
}
|
|
return undef unless $cnt;
|
|
my $sqdev = 1.0 / $cnt * ( $sqsum - $sum**2 / $cnt );
|
|
return $sqdev < 0.0 ? 0.0 : sqrt($sqdev);
|
|
}
|
|
|
|
|
|
|
|
1;
|
|
|
|
__END__
|
|
|
|
=head1 COPYRIGHT
|
|
|
|
Copyright 2007 by Tobias Oetiker
|
|
|
|
=head1 LICENSE
|
|
|
|
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.
|
|
|
|
You should have received a copy of the GNU General Public
|
|
License along with this program; if not, write to the Free
|
|
Software Foundation, Inc., 675 Mass Ave, Cambridge, MA
|
|
02139, USA.
|
|
|
|
=head1 AUTHOR
|
|
|
|
Tobias Oetiker E<lt>tobi@oetiker.chE<gt>
|
|
|
|
=cut
|