.. _auto_curve_segmented_linear_fit:

*PERFORM A LINEAR FIT AND RETURN THE SLOPES*
============================================

Fits a curve with one or more piecewise-linear (or secant) segments and returns the resulting slope(s) and fit statistics as a dataset. Use this worker to extract stiffness regions, identify multi-phase behaviour, or characterise yield transitions from any X-Y curve.

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

Classification: **process**.

Tagged: ``curve_fit``, ``linear_regression``, ``piecewise_linear``, ``r2``, ``secant``, ``segmented_linear_fit``, ``segments``, ``slope``.

Inputs
------

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

   * - Label
     - ID
     - Type
     - Default
     - Required
     - Description
   * - Curve
     - curve
     - vector
     - —
     - 
     - Input X-Y curve (vector pair) to be segmented and fitted; accepts any unit-consistent curve, e.g. force-displacement or stress-strain.
   * - Number Of Segments
     - numberof_segments
     - scalar
     - 1
     - 
     - Maximum number of piecewise linear segments to fit; integer ≥ 1, defaults to 1 (single global linear fit).
   * - R2 Limit
     - r2limit
     - scalar
     - 1
     - 
     - R² threshold in the range (0, 1] below which the segmentation algorithm stops adding a new segment; default 1.0 (fits until all segments are used).
   * - Min Percentage Of Points
     - minpercentageof_points
     - scalar
     - 1
     - 
     - Minimum fraction of total curve points (0–1 scale) that must be consumed by the current segment before the R² stopping criterion is evaluated; prevents trivially short segments from terminating the fit prematurely.
   * - Fit Type
     - fittype
     - scalar
     - linear
     - 
     - Fitting method: 'linear' uses ordinary least-squares regression (default), 'secant' forces the fit line through the actual data endpoints of each segment.

Outputs
-------

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

   * - Label
     - ID
     - Type
     - Description
   * - curve_segmented_linear_fit_output_1
     - curve_segmented_linear_fit_output_1
     - dataset
     - Dataset table containing one row per fitted segment with columns for segment index, start/end X values, slope, intercept, and R² goodness-of-fit score.

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

- ai_ml.supervised.regression
- data.curve.transform
- engineering.material.characterization

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

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

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   Auto-generated from <code>transformation</code> schema. Worker id: <code>curve_segmented_linear_fit</code>. Schema hash: <code>780293f405e2</code>. Hand-curated docs in <code>workerexamples/</code> override this page when present.
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