.. DO NOT EDIT. .. THIS FILE WAS AUTOMATICALLY GENERATED BY SPHINX-GALLERY. .. TO MAKE CHANGES, EDIT THE SOURCE PYTHON FILE: .. "gallery/Polygons/NCL_polyg_4.py" .. LINE NUMBERS ARE GIVEN BELOW. .. only:: html .. note:: :class: sphx-glr-download-link-note :ref:`Go to the end ` to download the full example code. .. rst-class:: sphx-glr-example-title .. _sphx_glr_gallery_Polygons_NCL_polyg_4.py: NCL_polyg_4.py ============== This script illustrates the following concepts: - Drawing a cylindrical equidistant map - Zooming in on a particular area on a cylindrical equidistant map - Attaching an outlined box to a map plot - Attaching filled polygons to a map plot - Filling in polygons with a shaded pattern - Changing the color and thickness of polylines - Changing the color of a filled polygon - Labeling the lines in a polyline - Changing the density of a fill pattern - Adding text to a plot See following URLs to see the reproduced NCL plot & script: - Original NCL script: https://www.ncl.ucar.edu/Applications/Scripts/polyg_4.ncl - Original NCL plot: https://www.ncl.ucar.edu/Applications/Images/polyg_4_1_lg.png and https://www.ncl.ucar.edu/Applications/Images/polyg_4_2_lg.png .. GENERATED FROM PYTHON SOURCE LINES 22-23 Import packages: .. GENERATED FROM PYTHON SOURCE LINES 23-33 .. code-block:: Python import numpy as np import xarray as xr import cartopy import cartopy.crs as ccrs import matplotlib.pyplot as plt import geocat.datafiles as gdf import geocat.viz as gv .. GENERATED FROM PYTHON SOURCE LINES 34-36 Read in data: ------------- .. GENERATED FROM PYTHON SOURCE LINES 36-40 .. code-block:: Python # Open a netCDF data file using xarray default engine and load the data into xarrays, choosing the 2nd timestamp ds = xr.open_dataset(gdf.get("netcdf_files/uv300.nc")).isel(time=1) .. GENERATED FROM PYTHON SOURCE LINES 41-43 Utility Function: Make Base Plot: --------------------------------- .. GENERATED FROM PYTHON SOURCE LINES 43-212 .. code-block:: Python # Define a utility function to create the basic contour plot, which will get used twice to create two slightly # different plots def make_base_plot(): # Generate axes using Cartopy projection ax = plt.axes(projection=ccrs.PlateCarree()) # Add continents continents = cartopy.feature.NaturalEarthFeature( name="coastline", category="physical", scale="50m", edgecolor="None", facecolor="lightgray", ) ax.add_feature(continents) # Set map extent ax.set_extent([-130, 0, -20, 40], crs=ccrs.PlateCarree()) # Define the contour levels. The top range value of 44 is not included in the levels. levels = np.arange(-12, 44, 4) # Using a dictionary prevents repeating the same keyword arguments twice for the contours. kwargs = dict( levels=levels, # contour levels specified outside this function xticks=[-120, -90, -60, -30, 0], # nice x ticks yticks=[-20, 0, 20, 40], # nice y ticks transform=ccrs.PlateCarree(), # ds projection add_colorbar=False, # don't add individual colorbars for each plot call add_labels=False, # turn off xarray's automatic Lat, lon labels colors="gray", # note plurals in this and following kwargs linestyles="-", linewidths=0.5, ) # Contourf-plot data (for filled contours) hdl = ds.U.plot.contour(x="lon", y="lat", ax=ax, **kwargs) # Add contour labels. Default contour labels are sparsely placed, so we specify label locations manually. # Label locations only need to be approximate; the nearest contour will be selected. label_locations = [ (-123, 35), (-116, 17), (-94, 4), (-85, -6), (-95, -10), (-85, -15), (-70, 35), (-42, 28), (-54, 7), (-53, -5), (-39, -11), (-28, 11), (-16, -1), (-8, -9), # Python allows trailing list separators. ] ax.clabel( hdl, fontsize="small", colors="black", fmt="%.0f", # Turn off decimal points manual=label_locations, # Manual label locations inline=False, ) # Don't remove the contour line where labels are located. # Create a rectangle patch, to color the border of the rectangle a different color. # Specify the rectangle as a corner point with width and height, to help place border text more easily. left, width = -90, 45 bottom, height = 0, 30 right = left + width top = bottom + height # Draw rectangle patch on the plot p = plt.Rectangle( (left, bottom), width, height, fill=False, zorder=3, # Plot on top of the purple box border. edgecolor='red', alpha=0.5, ) # Lower color intensity. ax.add_patch(p) # Draw text labels around the box. # Change the default padding around a text box to zero, making it a "tight" box. # Create "text_args" to keep from repeating code when drawing text. text_shared_args = dict( fontsize=8, bbox=dict(boxstyle='square, pad=0', facecolor='white', edgecolor='white'), ) # Draw top text ax.text( left + 0.6 * width, top, 'test', horizontalalignment='right', verticalalignment='center', **text_shared_args, ) # Draw bottom text. Change text background to match the map. ax.text( left + 0.5 * width, bottom, 'test', horizontalalignment='right', verticalalignment='center', fontsize=8, bbox=dict( boxstyle='square, pad=0', facecolor='lightgrey', edgecolor='lightgrey' ), ) # Draw left text ax.text( left, top, 'test', horizontalalignment='center', verticalalignment='top', rotation=90, **text_shared_args, ) # Draw right text ax.text( right, bottom, 'test', horizontalalignment='center', verticalalignment='bottom', rotation=-90, **text_shared_args, ) # Add lower text box. Box appears off-center, but this is to leave room # for lower-case letters that drop lower. ax.text( 1.0, -0.20, "CONTOUR FROM -12 TO 40 BY 4", fontname='Helvetica', horizontalalignment='right', transform=ax.transAxes, bbox=dict(boxstyle='square, pad=0.15', facecolor='white', edgecolor='black'), ) # Use geocat.viz.util convenience function to add main title as well as titles to left and right of the plot axes. gv.set_titles_and_labels( ax, lefttitle="Zonal Wind", lefttitlefontsize=12, righttitle="m/s", righttitlefontsize=12, ) # Use geocat.viz.util convenience function to add minor and major tick lines gv.add_major_minor_ticks(ax, y_minor_per_major=4) # Use geocat.viz.util convenience function to make plots look like NCL plots by using latitude, longitude tick labels gv.add_lat_lon_ticklabels(ax) return ax .. GENERATED FROM PYTHON SOURCE LINES 213-215 Plot 1 (Text inside a box): --------------------------- .. GENERATED FROM PYTHON SOURCE LINES 215-225 .. code-block:: Python # Create the base figure ax = make_base_plot() # Draw text inside of box ax.text(-60.0, 15.0, "sample", fontsize=11, horizontalalignment='center') # Show the plot plt.show() .. image-sg:: /gallery/Polygons/images/sphx_glr_NCL_polyg_4_001.png :alt: Zonal Wind, m/s :srcset: /gallery/Polygons/images/sphx_glr_NCL_polyg_4_001.png :class: sphx-glr-single-img .. GENERATED FROM PYTHON SOURCE LINES 226-228 Utility Function: Draw Hatch Polygon: ------------------------------------- .. GENERATED FROM PYTHON SOURCE LINES 228-257 .. code-block:: Python # Define a utility function that draws a polygon and then erases its border with another polygon. def draw_hatch_polygon(xvals, yvals, hatchcolor, hatchpattern): """Draw a polygon filled with a hatch pattern, but with no edges on the polygon.""" ax.fill( xvals, yvals, edgecolor=hatchcolor, zorder=-1, # Place underneath contour map (larger zorder is closer to viewer). fill=False, linewidth=0.5, hatch=hatchpattern, alpha=0.3, # Reduce color intensity ) # Hatch color and polygon edge color are tied together, so we have to draw a white polygon edge # on top of the original polygon to remove the edge. ax.fill( xvals, yvals, edgecolor='white', zorder=0, # Place on top of other polygon (larger zorder is closer to viewer). fill=False, linewidth=1, # Slightly larger linewidth removes ghost edges. ) .. GENERATED FROM PYTHON SOURCE LINES 258-260 Plot 2 (Polygons with hatch patterns): -------------------------------------- .. GENERATED FROM PYTHON SOURCE LINES 260-295 .. code-block:: Python # Make this figure the thumbnail image on the HTML page. # sphinx_gallery_thumbnail_number = 2 # Create the base figure ax = make_base_plot() # Plot the hatch pattern "underneath" the red box, to hide the purple border that is unavoidably attached to producing # the hatch pattern. x_points = [-90.0, -45.0, -45.0, -90.0, -90.0] y_points = [30.0, 30.0, 0.0, 0.0, 30.0] ax.fill( x_points, y_points, edgecolor='purple', # Box hatch pattern is purple. zorder=2, # Place on top of map (larger zorder is closer to viewer). fill=False, hatch='...', # Adding more or fewer dots to '...' will change hatch density. linewidth=0.5, # Make each dot smaller alpha=0.2, # Make hatch semi-transparent using alpha level in range [0, 1]. ) # Draw some triangles with various hatch pattern densities. x_tri = np.array([-125, -115, -120]) y_tri = np.array([-15, -10, 5]) draw_hatch_polygon(x_tri, y_tri, 'brown', '++++') draw_hatch_polygon(x_tri + 10, y_tri, 'blue', '+++') draw_hatch_polygon(x_tri + 20, y_tri, 'forestgreen', '++') # Show the plot plt.show() .. image-sg:: /gallery/Polygons/images/sphx_glr_NCL_polyg_4_002.png :alt: Zonal Wind, m/s :srcset: /gallery/Polygons/images/sphx_glr_NCL_polyg_4_002.png :class: sphx-glr-single-img .. rst-class:: sphx-glr-timing **Total running time of the script:** (0 minutes 0.305 seconds) .. _sphx_glr_download_gallery_Polygons_NCL_polyg_4.py: .. only:: html .. container:: sphx-glr-footer sphx-glr-footer-example .. container:: sphx-glr-download sphx-glr-download-jupyter :download:`Download Jupyter notebook: NCL_polyg_4.ipynb ` .. container:: sphx-glr-download sphx-glr-download-python :download:`Download Python source code: NCL_polyg_4.py ` .. container:: sphx-glr-download sphx-glr-download-zip :download:`Download zipped: NCL_polyg_4.zip ` .. only:: html .. rst-class:: sphx-glr-signature `Gallery generated by Sphinx-Gallery `_