.. DO NOT EDIT.
.. THIS FILE WAS AUTOMATICALLY GENERATED BY SPHINX-GALLERY.
.. TO MAKE CHANGES, EDIT THE SOURCE PYTHON FILE:
.. "gallery/XY/NCL_xy_5.py"
.. LINE NUMBERS ARE GIVEN BELOW.

.. only:: html

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

        :ref:`Go to the end <sphx_glr_download_gallery_XY_NCL_xy_5.py>`
        to download the full example code.

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

.. _sphx_glr_gallery_XY_NCL_xy_5.py:


NCL_xy_5.py
===============
This script illustrates the following concepts:
   - Draw multiple curves on an XY plot
   - Drawing a Y reference line in an XY plot
   - Filling the areas of an XY curve above and below a reference line
   - Using named colors to indicate a fill color
   - Converting dates from YYYYMM format to floats
   - Creating a main title
   - Setting the minimum/maximum value of the Y axis in an XY plot

See following URLs to see the reproduced NCL plot & script:
    - Original NCL script: https://www.ncl.ucar.edu/Applications/Scripts/xy_5.ncl
    - Original NCL plot: https://www.ncl.ucar.edu/Applications/Images/xy_5_1_lg.png

.. GENERATED FROM PYTHON SOURCE LINES 19-20

Import packages:

.. GENERATED FROM PYTHON SOURCE LINES 20-28

.. code-block:: Python


    import numpy as np
    import xarray as xr
    import matplotlib.pyplot as plt

    import geocat.datafiles as gdf
    import geocat.viz as gv








.. GENERATED FROM PYTHON SOURCE LINES 29-30

Read in data:

.. GENERATED FROM PYTHON SOURCE LINES 30-47

.. code-block:: Python


    # Open a netCDF data file using xarray default engine and load the data into xarrays
    ds = xr.open_dataset(gdf.get("netcdf_files/soi.nc"))
    dsoik = ds.DSOI_KET
    dsoid = ds.DSOI_DEC
    date = ds.date
    num_months = np.shape(date)[0]

    # Dates in the file are represented by year and month (YYYYMM)
    # representing them fractionally will make plotting the data easier
    # This produces the same results as NCL's yyyymm_to_yyyyfrac() function
    date_frac = np.empty_like(date)
    for n in np.arange(0, num_months, 1):
        yyyy = int(date[n] / 100)
        mon = (date[n] / 100 - yyyy) * 100
        date_frac[n] = yyyy + (mon - 1) / 12








.. GENERATED FROM PYTHON SOURCE LINES 48-49

Plot:

.. GENERATED FROM PYTHON SOURCE LINES 49-83

.. code-block:: Python


    # Generate figure (set its size (width, height) in inches) and axes
    plt.figure(figsize=(8, 4))
    ax = plt.gca()

    # Plot reference line
    ax.axhline(y=0, color='grey', linewidth=0.75)

    # Plot data
    # _labels=False prevents axis labels from being drawn
    ax.plot(date_frac, dsoik, color='black', linewidth=0.5)
    ax.plot(date_frac, dsoid, color='black')

    # Fill above and below the 0 line
    ax.fill_between(date_frac, dsoik, where=dsoik > 0, color='red')
    ax.fill_between(date_frac, dsoik, where=dsoik < 0, color='blue')

    # Use geocat.viz.util convenience function to add minor and major tick lines
    gv.add_major_minor_ticks(ax, x_minor_per_major=4, y_minor_per_major=5, labelsize=14)

    # Use geocat.viz.util convenience function to set axes parameters
    gv.set_axes_limits_and_ticks(
        ax,
        ylim=(-3, 3),
        yticks=np.linspace(-3, 3, 7),
        yticklabels=np.linspace(-3, 3, 7),
        xlim=(date_frac[0], date_frac[-1]),
        xticks=np.linspace(1880, 1980, 6),
    )

    # Use geocat.viz.util convenience function to set titles and labels
    gv.set_titles_and_labels(ax, maintitle="Darwin Southern Oscillation Index")

    plt.show()



.. image-sg:: /gallery/XY/images/sphx_glr_NCL_xy_5_001.png
   :alt: Darwin Southern Oscillation Index
   :srcset: /gallery/XY/images/sphx_glr_NCL_xy_5_001.png
   :class: sphx-glr-single-img






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

   **Total running time of the script:** (0 minutes 0.685 seconds)


.. _sphx_glr_download_gallery_XY_NCL_xy_5.py:

.. only:: html

  .. container:: sphx-glr-footer sphx-glr-footer-example

    .. container:: sphx-glr-download sphx-glr-download-jupyter

      :download:`Download Jupyter notebook: NCL_xy_5.ipynb <NCL_xy_5.ipynb>`

    .. container:: sphx-glr-download sphx-glr-download-python

      :download:`Download Python source code: NCL_xy_5.py <NCL_xy_5.py>`

    .. container:: sphx-glr-download sphx-glr-download-zip

      :download:`Download zipped: NCL_xy_5.zip <NCL_xy_5.zip>`


.. only:: html

 .. rst-class:: sphx-glr-signature

    `Gallery generated by Sphinx-Gallery <https://sphinx-gallery.github.io>`_