NAME

       anomaly - anomalous data detection

SYNOPSIS

       anomaly [-h|--help] [-v|--version] [-d|--details]
               [-t|--threshold] [--min N] [--max N]
               [-s|--stddev] [-n|--sample N] [-c|--coefficient N]
               [-q|--quiet]
               [-e|--execute PROGRAM]
               [-p|--pid PID]

DESCRIPTION

       Anomaly  can  detect  anomalous  data  in  a numeric stream.  In order to do this, anomaly needs to see a
       stream of numeric data, and apply one of its detection methods.  If an anomaly is detected, a response is
       made, chosen from one or more built in methods.

NUMERIC STREAM

       Anomaly  works  best  in  a  pipe,  and will read only numeric data from its input.  As a simple example,
       suppose you wish to monitor load average and look for unusual spikes.  The load average can  be  obtained
       from the 'uptime' command:

              $ uptime
              11:40  up 15 days,  4:04, 6 users, load averages: 0.38 0.32 0.32

       We can extract the 5-minute load (the second of the three numbers) using this:

              $ uptime | cut -f 13 -d ' '
              0.29

       That number can be extracted once a minute, using this:

              $ while [ 1 ]; do uptime | cut -f 13 -d ' '; sleep 60; done
              0.29
              0.26
              0.19

       That  is the kind of data stream that anomaly monitors.  White space (spaces, tabs, newlines) between the
       numbers are ignored, so we can simulate the above stream like this:

              $ echo 0.29 0.26 0.19

       This is a convenient way to demonstrate anomaly, shown below.

DETECTION - THRESHOLD

       The simplest detection method is threshold, which compares the data to an absolute  value.   This  method
       can  use a minimum and a maximum value for comparison.  These alternatives are all valid, and make use of
       --min, --max or both:

              anomaly --threshold --min 1.22 --max 9.75
              anomaly --threshold --min 1.22
              anomaly --threshold --max 9.75

       In the following example, the values '1' and '10' would be detected as anomalies:

              $ echo 2 1 3 6 10 5 | anomaly --threshold --min 1.5 --max 8
              Anomalous data detected.  The value 1 is below the minimum of 1.5.
              Anomalous data detected.  The value 10 is above the maximum of 8.

DETECTION - STANDARD DEVIATION

       Standard deviation measures differences from the mean value of a  sample  of  data,  and  is  useful  for
       detecting  extraordinary  values.   The  sample  size  can  be  chosen  such that there is enough data to
       determine a good mean value, but defaults to 10.  The limited sample size means that a rolling window  of
       data  is  used,  and  therefore  the mean and standard deviation is updated for the current window.  This
       makes the monitoring somewhat adaptive.  Here is an example:

              anomaly --stddev --sample 20

       This uses a sample size of the 20 most recent values, and will detect any values that are +/- 1  standard
       deviation from the mean.  An example:

              $ echo 1 2 3 4 5 6 | anomaly --stddev --sample 5
              Anomalous  data  detected.   The  value  6  is more than 1 sigma(s) above the mean value 3, with a
              sample size of 5.

       With a sample size of 5, comparisons being only after the 6th value is seen.  In the  example,  the  mean
       value  of  [1  2  3  4  5]  is  3,  and the standard deviation is 1.58.  This means that the 6th value is
       considered an anomaly if it is within the range (3 +/- 1.58), which is between 1.42 and 4.58.

       To make this less sensitive, a coefficient is introduced, which defaults to 1.0 (as  above)  but  can  be
       overridden:

              $ echo 1 2 3 4 5 6 | anomaly --stddev --sample 5 --coefficient 1.9
              $

       In  this example, the 6th value is not considered an anomaly because it is within the range (3 +/- (1.9 *
       1.58)), which is between -0.002 and 6.002.

RESPONSE - MESSAGE

       The message response is the default, and consists of a single line of printed text.  It is a  description
       of why the data value is considered an anomaly.  Here is an example:

              $ echo 1 2 3 | anomaly --threshold --max 2.5
              Anomalous data detected.  The value 3 is above the maximum of 2.5.

       The  message  can  be  suppressed,  but another response must be specified, so that there is some kind of
       response:

              $ echo 1 2 3 | anomaly --threshold --max 2.5 --quiet ...

RESPONSE - EXECUTE

       Anomaly can execute a program in response to detection.  Here an example uses the 'date' command, but any
       program can be used:

              $ echo 1 2 3 | anomaly --threshold --max 2.5 --quiet --execute '/bin/date +%s'
              1361727327

RESPONSE - SIGNAL

       Anomaly can send a USR1 signal to a program in response to detection:

              $ echo 1 2 3 | anomaly --threshold --max 2.5 --quiet --pid 12345

       This  sends  the  USR1 signal to the process with PID 12345.  The receiving program would need to respond
       accordingly.

CREDITS & COPYRIGHTS

       Copyright (C) 2013 Göteborg Bit Factory.

       Anomaly is distributed under the MIT license. See http://www.opensource.org/licenses/mit-license.php  for
       more information.

SEE ALSO

       For more information, see:

       The official site at
              <http://tasktools.org/projects/anomaly>

       You can contact the project by writing an email to
              <support@tasktools.org>

REPORTING BUGS

       Bugs in anomaly may be reported to <support@tasktools.org>

${PACKAGE_STRING}                                  2013-05-05                                         anomaly(1)