.. _auto_curve_area_above_baseline:

*AREA BETWEEN A CURVE AND A BASELINE*
=====================================

Computes the trapezoidal area between a curve and a baseline over an X range. The baseline can be the straight chord between the X limits (DSC peak energy / hysteresis loop convention), the X axis, or a horizontal line at a chosen Y value. Crossing handled by zero-split when area mode is 'absolute', so the result matches a fine-grained hand calculation.

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

Classification: **process**.

Tagged: ``ASTM_E2070``, ``DSC``, ``area_above_baseline``, ``baseline_subtraction``, ``chord``, ``curve_integral``, ``enclosed_area``, ``hysteresis``.

Inputs
------

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

   * - Label
     - ID
     - Type
     - Default
     - Required
     - Description
   * - Curve
     - curve
     - vector
     - —
     - 
     - Input XY curve. The area returned is the integral of (Curve minus baseline) between the X limits.
   * - X Left
     - x_left
     - string
     - —
     - 
     - Left X integration limit. Leave blank to use the curve's left endpoint.
   * - X Right
     - x_right
     - string
     - —
     - 
     - Right X integration limit. Leave blank to use the curve's right endpoint.
   * - Baseline Mode
     - baseline_mode
     - select
     - endpoints
     - 
     - 'Endpoints' draws a straight baseline from (X Left, y(X Left)) to (X Right, y(X Right)) and integrates the curve minus that line; this is the DSC / ASTM E2070 convention for peak energy and applies to hysteresis loops, transition energies, and any 'area above a chord' calculation. 'Y=0' integrates against the X axis (curve minus zero) over the X range. 'Horizontal' integrates against the constant Y value set in 'Y Baseline'.
   * - Y Baseline
     - y_baseline
     - string
     - 0
     - 
     - Constant Y value used as the baseline when Baseline Mode is 'Horizontal'. Ignored otherwise.
   * - Area Mode
     - area_mode
     - select
     - signed
     - 
     - 'Signed' returns the net trapezoidal integral of (curve - baseline); regions where the curve dips below the baseline subtract from the total. 'Absolute' returns the integral of the absolute difference; sign changes within a segment are handled by splitting that segment at the zero crossing so the answer matches a fine-grained hand calculation.

Outputs
-------

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

   * - Label
     - ID
     - Type
     - Description
   * - curve_area_above_baseline_output_1
     - curve_area_above_baseline_output_1
     - scalar
     - Scalar area in natural units of X x Y. With Baseline Mode = 'Endpoints' this is the ASTM E2070 peak energy or hysteresis area between the chord and the curve; with 'Y=0' it is the ordinary integral of the curve; with 'Horizontal' it is the integral above a constant Y line.

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

- data.curve.transform
- data.statistics
- engineering.material.characterization
- engineering.thermal_analysis

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

A runnable example is registered for this worker. Open the example workflow on the d3VIEW canvas: `/api/workflow/example?id=cs_432_area_between_curves <https://www.d3view.com/api/workflow/example?id=cs_432_area_between_curves>`_

.. raw:: html

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