working_with_panel.py

"""
Interactive data visualization using ``Panel``
==============================================

.. note::

    Please run the following code examples in a notebook environment
    otherwise the interactive parts of this tutorial will not work. You can
    use the button "Download Jupyter notebook" at the bottom of this page
    to download this script as a Jupyter notebook.

The library `Panel <https://panel.holoviz.org/index.html>`__ can be used to
create interactive dashboards by connecting user-defined widgets to plots.
``Panel`` can be used as an extension to Jupyter notebook/lab.

This tutorial is split into three parts:

- Make a static map
- Make an interactive map
- Add a grid for Earth relief
"""

# %%
# Import the required packages
import numpy as np
import panel as pn
import pygmt

pn.extension()


# %%
# Make a static map
# -----------------
#
# The `Orthographic projection
# <https://www.pygmt.org/dev/projections/azim/azim_orthographic.html>`__
# can be used to show the Earth as a globe. Land and water masses are
# filled with colors via the ``land`` and  ``water`` parameters of
# :meth:`pygmt.Figure.coast`, respectively. Coastlines are added using the
# ``shorelines`` parameter.

# Create a new instance or object of the pygmt.Figure() class
fig = pygmt.Figure()
fig.coast(
    # Orthographic projection (G) with projection center at 0° East and
    # 15° North and a width of 12 centimeters
    projection="G0/15/12c",
    region="g",  # global
    frame="g30",  # Add frame and gridlines in steps of 30 degrees on top
    land="gray",  # Color land masses in "gray"
    water="lightblue",  # Color water masses in "lightblue"
    # Add coastlines with a 0.25-point thick pen in "gray50"
    shorelines="1/0.25p,gray50",
)
fig.show()


# %%
# Make an interactive map
# -----------------------
#
# To generate a rotation of the Earth around the vertical axis, the central
# longitude of the Orthographic projection is varied iteratively in steps of
# 10 degrees. The library ``Panel`` is used to create an interactive dashboard
# with a slider (works only in a notebook environment, e.g., Jupyter notebook).

# Create a slider
slider_lon = pn.widgets.DiscreteSlider(
    name="Central longitude",  # Give name for quantity shown at the slider
    options=list(np.arange(0, 361, 10)),  # Range corresponding to longitude
    value=0,  # Set start value
)


@pn.depends(central_lon=slider_lon)
def view(central_lon):
    """
    Define a function for plotting the single slices.
    """
    # Create a new instance or object of the pygmt.Figure() class
    fig = pygmt.Figure()
    fig.coast(
        # Vary the central longitude used for the Orthographic projection
        projection=f"G{central_lon}/15/12c",
        region="g",
        frame="g30",
        land="gray",
        water="lightblue",
        shorelines="1/0.25p,gray50",
    )
    return fig


# Make an interactive dashboard
pn.Column(slider_lon, view)


# %%
# Add a grid for Earth relief
# ---------------------------
#
# Instead of using colors as fill for the land and water masses a grid can be
# displayed. Here, the Earth relief is shown by color-coding the elevation.

# Download a grid for Earth relief with a resolution of 10 arc-minutes
grd_relief = pygmt.datasets.load_earth_relief(resolution="10m")

# Create a slider
slider_lon = pn.widgets.DiscreteSlider(
    name="Central longitude",
    options=list(np.arange(0, 361, 10)),
    value=0,
)


@pn.depends(central_lon=slider_lon)
def view(central_lon):
    """
    Define a function for plotting the single slices.
    """
    # Create a new instance or object of the pygmt.Figure() class
    fig = pygmt.Figure()
    # Set up a colormap for the elevation in meters
    pygmt.makecpt(
        cmap="SCM/oleron",
        # minimum, maximum, step
        series=[int(grd_relief.data.min()) - 1, int(grd_relief.data.max()) + 1, 100],
    )
    # Plot the grid for the elevation
    fig.grdimage(
        projection=f"G{central_lon}/15/12c",
        region="g",
        grid=grd_relief,  # Use grid downloaded above
        cmap=True,  # Use colormap defined above
        frame="g30",
    )
    # Add a horizontal colorbar for the elevation.
    fig.colorbar(annot=2000, tick=1000, label="Elevation", unit="m")
    return fig


# Make an interactive dashboard
pn.Column(slider_lon, view)

# sphinx_gallery_thumbnail_number = 1