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| author | Tobi Oetiker <tobi@oetiker.ch> | 2007-09-11 08:12:01 +0200 |
|---|---|---|
| committer | Tobi Oetiker <tobi@oetiker.ch> | 2007-09-11 08:12:01 +0200 |
| commit | 3586889c03cae00263de98129b1662e9abc7b14a (patch) | |
| tree | 4fd7ee65bf78c5b254b4037bca73a2dfb64c1098 | |
| parent | fa5abd5d25b193c47400f116c852c0a0b176322a (diff) | |
| download | smokeping-3586889c03cae00263de98129b1662e9abc7b14a.tar.gz smokeping-3586889c03cae00263de98129b1662e9abc7b14a.tar.xz | |
rounding error fix for sqrt
| -rw-r--r-- | CHANGES | 2 | ||||
| -rw-r--r-- | lib/Smokeping/RRDhelpers.pm | 3 |
2 files changed, 4 insertions, 1 deletions
@@ -1,3 +1,5 @@ +* fixed problem with rounding error in calculating stddev + 2007/9/06 -- released version 2.2.3 * alter ajax grapher mode to use seconds timestamps and not iso dates this prevents timezone problems with the browser -- tobi diff --git a/lib/Smokeping/RRDhelpers.pm b/lib/Smokeping/RRDhelpers.pm index 3f4fa5b..e491a5c 100644 --- a/lib/Smokeping/RRDhelpers.pm +++ b/lib/Smokeping/RRDhelpers.pm @@ -52,7 +52,8 @@ sub get_stddev{ } } return undef unless $cnt; - return sqrt( 1.0 / $cnt * ( $sqsum - $sum**2 / $cnt )) + my $sqdev = 1.0 / $cnt * ( $sqsum - $sum**2 / $cnt ); + return $sqdev < 0.0 ? 0.0 : sqrt($sqdev); } |