.. _auto_curve_event_detection_sign_change:

*DETECT SIGN CHANGES BASED SIGN CHANGE*
=======================================

Scans a time-series curve for sign-change events (positive-to-negative or negative-to-positive zero crossings) subject to configurable minimum/maximum duration windows, fluctuation tolerance, and amplitude thresholds. Use this worker to isolate sustained polarity-reversal events in signals such as force, velocity, or displacement histories.

When to use
-----------

Classification: **process**.

Tagged: ``curve``, ``event_detection``, ``sign_change``, ``signal``, ``time_series``, ``transformations``, ``zero_crossing``.

Inputs
------

.. list-table::
   :header-rows: 1
   :widths: 20 20 20 20 20 20

   * - Label
     - ID
     - Type
     - Default
     - Required
     - Description
   * - Curve
     - curve
     - vector
     - —
     - 
     - Input time-series curve (X = time, Y = signal value) on which sign-change event detection is performed; accepts any real-valued vector curve.
   * - Check Type
     - changetype
     - list
     - positive_to_negative
     - 
     - Direction of the sign change to detect: 'positive_to_negative' (default) or 'negative_to_positive'; selects which zero-crossing polarity triggers an event.
   * - Min Time Window
     - pretime_window
     - scalar
     - 600
     - 
     - Minimum duration (in curve time units, default 600) over which the sign change must be sustained before it is registered as a valid event.
   * - Max Time Window
     - posttime_window
     - scalar
     - 1200
     - 
     - Maximum duration (in curve time units, default 1200) allowed for a single event; if the crossing persists beyond this value the detector resets and searches for the next event.
   * - Fluctuation Time Window
     - fluctuationtimewindowinpercentage
     - scalar
     - 2%
     - 
     - Short grace window (expressed as a percentage of the minimum time window, default '2%') within which minor signal fluctuations back across zero are ignored so that noisy crossings are not split into multiple events.
   * - Minimum Cycle Max
     - minimum_cycle_maxpercentageof_total_max
     - scalar
     - 5%
     - 
     - Minimum cycle change in percentage of the sustained max value
   * - Include All Cross-over Points
     - includeallcross-overpoints
     - list
     - no
     - 
     - Include all cross-over points
   * - Zero Value
     - zerovalue
     - scalar
     - 1.0
     - 
     - Values within -1.0 and 1.0 of this value is considered zero
   * - Project Values Within The Zero Value
     - projectvalueswithinthezerovalue
     - list
     - no
     - 
     - Project points whose y-value fall within the zero value to zero

Outputs
-------

.. list-table::
   :header-rows: 1
   :widths: 20 20 20 20

   * - Label
     - ID
     - Type
     - Description
   * - curve_event_detection_sign_change_output_1
     - curve_event_detection_sign_change_output_1
     - dataset
     - Dataset table listing each detected sign-change event with its start time, end time, duration, and relevant amplitude statistics extracted from the input curve.

Disciplines
-----------

- data.curve.transform
- data.signal_processing

Runnable example
----------------

A runnable example is registered for this worker. Open the example workflow on the d3VIEW canvas: `/api/workflow/example?id=curve_event_detection_sign_change <https://www.d3view.com/api/workflow/example?id=curve_event_detection_sign_change>`_

.. raw:: html

   <hr style="margin-top:2em">
   <p style="font-size:11px;color:#888">
   Auto-generated from <code>transformation</code> schema. Worker id: <code>curve_event_detection_sign_change</code>. Schema hash: <code>70fe94dbff4d</code>. Hand-curated docs in <code>workerexamples/</code> override this page when present.
   </p>