How to use the metpy.plots.StationPlot function in MetPy

def test_barb_no_default_unit_conversion():
    """Test that barbs units are left alone by default (#737)."""
    x_pos = np.array([0])
    y_pos = np.array([0])
    u_wind = np.array([3.63767155210412]) * units('m/s')
    v_wind = np.array([3.63767155210412]) * units('m/s')

    fig = plt.figure()
    ax = fig.add_subplot(1, 1, 1)
    stnplot = StationPlot(ax, x_pos, y_pos)
    stnplot.plot_barb(u_wind, v_wind)
    ax.set_xlim(-5, 5)
    ax.set_ylim(-5, 5)

    return fig

def test_barb_unit_conversion(barbs_units):
    """Test that barbs units can be converted at plot time (#737)."""
    x_pos, y_pos, u_wind, v_wind = barbs_units

    fig = plt.figure()
    ax = fig.add_subplot(1, 1, 1)
    stnplot = StationPlot(ax, x_pos, y_pos)
    stnplot.plot_barb(u_wind, v_wind, plot_units='knots')
    ax.set_xlim(-5, 5)
    ax.set_ylim(-5, 5)

    return fig

def test_station_plot_replace():
    """Test that locations are properly replaced."""
    fig = plt.figure(figsize=(3, 3))

    # testing data
    x = np.array([1])
    y = np.array([1])

    # Make the plot
    sp = StationPlot(fig.add_subplot(1, 1, 1), x, y, fontsize=16)
    sp.plot_barb([20], [0])
    sp.plot_barb([5], [0])
    sp.plot_parameter('NW', [10.5], color='red')
    sp.plot_parameter('NW', [20], color='blue')

    sp.ax.set_xlim(-3, 3)
    sp.ax.set_ylim(-3, 3)

    return fig

def test_arrow_unit_conversion(barbs_units):
    """Test that arrow units can be converted at plot time (#737)."""
    x_pos, y_pos, u_wind, v_wind = barbs_units

    fig = plt.figure()
    ax = fig.add_subplot(1, 1, 1)
    stnplot = StationPlot(ax, x_pos, y_pos)
    stnplot.plot_arrow(u_wind, v_wind, plot_units='knots')
    ax.set_xlim(-5, 5)
    ax.set_ylim(-5, 5)

    return fig

def test_barb_projection(wind_plot):
    """Test that barbs are properly projected (#598)."""
    u, v, x, y = wind_plot

    # Plot and check barbs (they should align with grid lines)
    fig = plt.figure()
    ax = fig.add_subplot(1, 1, 1, projection=ccrs.LambertConformal())
    ax.gridlines(xlocs=[-135, -120, -105, -90, -75, -60, -45])
    sp = StationPlot(ax, x, y, transform=ccrs.PlateCarree())
    sp.plot_barb(u, v)

    return fig

def test_barb_unit_conversion_exception(u, v):
    """Test that errors are raise if unit conversion is requested on un-united data."""
    x_pos = np.array([0])
    y_pos = np.array([0])

    fig = plt.figure()
    ax = fig.add_subplot(1, 1, 1)
    stnplot = StationPlot(ax, x_pos, y_pos)
    with pytest.raises(ValueError):
        stnplot.plot_barb(u, v, plot_units='knots')

def test_station_layout_odd_data():
    """Test more corner cases with data passed in."""
    fig = plt.figure(figsize=(9, 9))

    # Set up test layout
    layout = StationPlotLayout()
    layout.add_barb('u', 'v')
    layout.add_value('W', 'temperature', units='degF')

    # Now only use data without wind and no units
    data = {'temperature': [25.]}

    # Make the plot
    sp = StationPlot(fig.add_subplot(1, 1, 1), [1], [2], fontsize=12)
    layout.plot(sp, data)
    assert True

ax.add_feature(cfeature.OCEAN)
ax.add_feature(cfeature.LAKES)
ax.add_feature(cfeature.COASTLINE)
ax.add_feature(cfeature.STATES)
ax.add_feature(cfeature.BORDERS)

# Set plot bounds
ax.set_extent((-118, -73, 23, 50))

#
# Here's the actual station plot
#

# Start the station plot by specifying the axes to draw on, as well as the
# lon/lat of the stations (with transform). We also the fontsize to 12 pt.
stationplot = StationPlot(ax, data['lon'].values, data['lat'].values, clip_on=True,
                          transform=ccrs.PlateCarree(), fontsize=12)

# Plot the temperature and dew point to the upper and lower left, respectively, of
# the center point. Each one uses a different color.
stationplot.plot_parameter('NW', data['air_temperature'], color='red')
stationplot.plot_parameter('SW', data['dew_point_temperature'],
                           color='darkgreen')

# A more complex example uses a custom formatter to control how the sea-level pressure
# values are plotted. This uses the standard trailing 3-digits of the pressure value
# in tenths of millibars.
stationplot.plot_parameter('NE', data['slp'], formatter=lambda v: format(10 * v, '.0f')[-3:])

# Plot the cloud cover symbols in the center location. This uses the codes made above and
# uses the `sky_cover` mapper to convert these values to font codes for the
# weather symbol font.

ax.add_feature(feat.OCEAN, zorder=-1)
ax.add_feature(feat.LAKES, zorder=-1)
ax.coastlines(resolution='110m', zorder=2, color='black')
ax.add_feature(state_boundaries, edgecolor='black')
ax.add_feature(feat.BORDERS, linewidth=2, edgecolor='black')

# Set plot bounds
ax.set_extent((-118, -73, 23, 50))

#
# Here's the actual station plot
#

# Start the station plot by specifying the axes to draw on, as well as the
# lon/lat of the stations (with transform). We also the fontsize to 12 pt.
stationplot = StationPlot(ax, data['longitude'], data['latitude'],
                          transform=ccrs.PlateCarree(), fontsize=12)

# The layout knows where everything should go, and things are standardized using
# the names of variables. So the layout pulls arrays out of `data` and plots them
# using `stationplot`.
simple_layout.plot(stationplot, data)

plt.show()

###########################################
# or instead, a custom layout can be used:

# Just winds, temps, and dewpoint, with colors. Dewpoint and temp will be plotted
# out to Farenheit tenths. Extra data will be ignored
custom_layout = StationPlotLayout()
custom_layout.add_barb('eastward_wind', 'northward_wind', units='knots')

ax.add_feature(feat.OCEAN, zorder=-1)
ax.add_feature(feat.LAKES, zorder=-1)
ax.coastlines(resolution='110m', zorder=2, color='black')
ax.add_feature(state_boundaries, edgecolor='black')
ax.add_feature(feat.BORDERS, linewidth=2, edgecolor='black')

# Set plot bounds
ax.set_extent((-118, -73, 23, 50))

#
# Here's the actual station plot
#

# Start the station plot by specifying the axes to draw on, as well as the
# lon/lat of the stations (with transform). We also the fontsize to 12 pt.
stationplot = StationPlot(ax, data['longitude'], data['latitude'],
                          transform=ccrs.PlateCarree(), fontsize=12)

# The layout knows where everything should go, and things are standardized using
# the names of variables. So the layout pulls arrays out of `data` and plots them
# using `stationplot`.
simple_layout.plot(stationplot, data)

plt.show()

###########################################
# or instead, a custom layout can be used:

# Just winds, temps, and dewpoint, with colors. Dewpoint and temp will be plotted
# out to Farenheit tenths. Extra data will be ignored
custom_layout = StationPlotLayout()
custom_layout.add_barb('eastward_wind', 'northward_wind', units='knots')