Plotting Scalar Quantities
==========================

The basic idea of Viscid is to convert data files to :class:`viscid.field.Field` objects and pass them to a convenience function for plotting. It is useful to note that Field objects have most of the same functionality as Numpy's `ndarrays`. That is, you can do simple math with Numpy using::

    field_momentum = field_density * field_velocity

Various shims for plotting fields using matplotlib are provided by :py:mod:`viscid.plot.vpyplot`. The functions are listed in :doc:`../functions`. For an enumeration of extra plotting keyword arguments, see :doc:`../plot_options`. Also, you can specify keyword arguments that are conusmed by the matplotlib function used to make the plot, i.e., `pyplot.pcolormesh`, `pyplot.contourf`, etc.

Plotting Temperature
--------------------

Here, we just open up an OpenGGCM xdmf file and plot the Temperature with a log scale. For a better idea of the different plotting options, refer to :doc:`../plot_options`.

.. plot::
    :include-source:

    from os import path

    import viscid
    from viscid.plot import vpyplot as vlt


    f3d = viscid.load_file(path.join(viscid.sample_dir, 'sample_xdmf.3d.xdmf'))

    pPa_to_dyne_per_cm2 = 1e-11
    erg_to_K = (1.380e-16)**-1
    fac = (2.0 / 3.0) * erg_to_K * pPa_to_dyne_per_cm2

    T = fac * f3d["pp"] / f3d["rr"]
    T.name = "T"
    T.pretty_name = "T (K)"

    vlt.plot(T['y=0j'], logscale=True, earth=True)

    vlt.show()

Two Plots, One Figure
---------------------

.. plot::
    :include-source:

    from os import path

    import viscid
    from viscid.plot import vpyplot as vlt
    from matplotlib import pyplot as plt


    f3d = viscid.load_file(path.join(viscid.sample_dir, 'sample_xdmf.3d.xdmf'))

    fig, axes = plt.subplots(2, 1, sharex=True, sharey=True)

    # plot pressure with 64 contours on a logscale
    vlt.plot(f3d["pp"]["y=0.0j"], style="contourf", levels=64,
             plot_opts="log, earth", ax=axes[0])

    # plot velocity in x with a colorbar symmetric about 0
    # also, share axes so this plot pans/zooms with the first
    vlt.plot(f3d["vx"]["y=0.0j"], style="contourf", levels=64,
             lin=0, earth=True, ax=axes[1])

    plt.xlim((-20, 20))
    plt.ylim((-10, 10))

    vlt.auto_adjust_subplots()

    vlt.show()