.. DO NOT EDIT.
.. THIS FILE WAS AUTOMATICALLY GENERATED BY SPHINX-GALLERY.
.. TO MAKE CHANGES, EDIT THE SOURCE PYTHON FILE:
.. "auto_tutorials/example_02_scalar_fields.py"
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.. only:: html

    .. note::
        :class: sphx-glr-download-link-note

        :ref:`Go to the end <sphx_glr_download_auto_tutorials_example_02_scalar_fields.py>`
        to download the full example code.

.. rst-class:: sphx-glr-example-title

.. _sphx_glr_auto_tutorials_example_02_scalar_fields.py:


Build and operate on a scalarField
==================================

By the end of this tutorial you will:

- construct a :class:`pybFoam.scalarField` from a NumPy array,
- view it back as a NumPy array (zero-copy),
- apply OpenFOAM elementwise operators (``sin``, ``*``, ``+``,
  in-place ``+=``) to it, and
- plot the result with matplotlib.

The point of this page is to show that ``scalarField`` is a real
OpenFOAM primitive, not a NumPy wrapper. The same operators dispatch
the same templated math that ``volScalarField`` uses inside a solver.

Prerequisites
-------------

- Finished :doc:`example_01_dictionaries`.

.. GENERATED FROM PYTHON SOURCE LINES 24-30

Build a scalarField from NumPy
------------------------------
Constructing :class:`pybFoam.scalarField` from a NumPy array copies
the data into OpenFOAM's memory once. From that point on,
``np.asarray(field)`` is a zero-copy view back to the same buffer —
any in-place edit is visible to OpenFOAM.

.. GENERATED FROM PYTHON SOURCE LINES 30-41

.. code-block:: Python


    import numpy as np

    from pybFoam import scalarField

    x = np.linspace(0.0, 1.0, 200)
    field = scalarField(x)

    print(f"len(field)        = {len(field)}")
    print(f"np.asarray(field) = {np.asarray(field)[:5]} ...")





.. rst-class:: sphx-glr-script-out

 .. code-block:: none

    len(field)        = 200
    np.asarray(field) = [0.         0.00502513 0.01005025 0.01507538 0.0201005 ] ...




.. GENERATED FROM PYTHON SOURCE LINES 42-44

Confirm zero-copy: edit through the view, see the update on the
field side.

.. GENERATED FROM PYTHON SOURCE LINES 44-50

.. code-block:: Python


    field_view = np.asarray(field)
    field_view[0] = 99.0
    print(f"field[0] after view edit = {field[0]}")
    field_view[0] = x[0]  # restore





.. rst-class:: sphx-glr-script-out

 .. code-block:: none

    field[0] after view edit = 99.0




.. GENERATED FROM PYTHON SOURCE LINES 51-56

Elementwise operators are real OpenFOAM ops
-------------------------------------------
Top-level functions like :func:`pybFoam.sin` take a ``scalarField``
and return a new one. ``+``, ``-``, ``*``, ``/`` are bound directly,
and there are in-place variants (``+=``, ``*=``) too.

.. GENERATED FROM PYTHON SOURCE LINES 56-65

.. code-block:: Python


    import pybFoam

    y = pybFoam.sin(field * np.pi) * 2.0 + 1.0
    y_np = np.asarray(y)

    print(f"y range  : {y_np.min():.4f} … {y_np.max():.4f}")
    print(f"y[50]    : {y_np[50]:.4f}   (analytic: {2 * np.sin(np.pi * x[50]) + 1:.4f})")





.. rst-class:: sphx-glr-script-out

 .. code-block:: none

    y range  : 1.0000 … 2.9999
    y[50]    : 2.4198   (analytic: 2.4198)




.. GENERATED FROM PYTHON SOURCE LINES 66-71

The min should sit close to ``-1`` (at :math:`x = 1.5/\pi`) and the
max close to ``3`` (at :math:`x = 0.5`). The point-wise check at the
middle of the range matches the analytic formula
:math:`2\sin(\pi x) + 1` to round-off — proof the operator chain
evaluated and not just round-tripped.

.. GENERATED FROM PYTHON SOURCE LINES 73-77

In-place variants
-----------------
Operators like ``+=`` modify the field's storage directly without
allocating a new buffer.

.. GENERATED FROM PYTHON SOURCE LINES 77-83

.. code-block:: Python


    z = scalarField(np.zeros_like(x))
    z += pybFoam.cos(field * np.pi)
    print(f"z[0]  = {np.asarray(z)[0]:.4f}   (cos 0 = 1)")
    print(f"z[-1] = {np.asarray(z)[-1]:.4f}   (cos π = -1)")





.. rst-class:: sphx-glr-script-out

 .. code-block:: none

    z[0]  = 1.0000   (cos 0 = 1)
    z[-1] = -1.0000   (cos π = -1)




.. GENERATED FROM PYTHON SOURCE LINES 84-89

Plot the result
---------------
A 1-D matplotlib line plot makes the shape of the operation
obvious. A flat or zero curve here would mean an operator did not
evaluate.

.. GENERATED FROM PYTHON SOURCE LINES 89-103

.. code-block:: Python


    import matplotlib.pyplot as plt

    fig, ax = plt.subplots(figsize=(6, 3))
    ax.plot(x, y_np, label=r"$2\sin(\pi x) + 1$")
    ax.plot(x, np.asarray(z), label=r"$\cos(\pi x)$", linestyle="--")
    ax.axhline(0.0, color="k", lw=0.5)
    ax.set_xlabel("x")
    ax.set_ylabel("scalarField value")
    ax.set_title("scalarField after pybFoam operators")
    ax.legend()
    ax.grid(alpha=0.3)
    fig.tight_layout()
    plt.show()



.. image-sg:: /auto_tutorials/images/sphx_glr_example_02_scalar_fields_001.png
   :alt: scalarField after pybFoam operators
   :srcset: /auto_tutorials/images/sphx_glr_example_02_scalar_fields_001.png
   :class: sphx-glr-single-img






.. rst-class:: sphx-glr-timing

   **Total running time of the script:** (0 minutes 0.174 seconds)


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.. only:: html

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      :download:`Download Python source code: example_02_scalar_fields.py <example_02_scalar_fields.py>`

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