Merge pull request #455 from NCAR/scatter_10

Scatter 10

Gallery/Scatter/NCL_scatter_10.py

@@ -0,0 +1,86 @@
+"""
+NCL_scatter_10.py
+=================
+This script illustrates the following concepts:
+   - Drawing a scatter plot over a map
+   - Customizing markers in a scatter plot
+   - Using numpy.random to generate random plot
+
+See following URLs to see the reproduced NCL plot & script:
+    - Original NCL script: https://www.ncl.ucar.edu/Applications/Scripts/scatter_10.ncl
+    - Original NCL plot: https://www.ncl.ucar.edu/Applications/Images/scatter_10_lg.png
+"""
+
+###############################################################################
+# Import packages:
+
+from unittest import load_tests
+import numpy as np
+import matplotlib.pyplot as plt
+import cartopy.crs as ccrs
+from cartopy.mpl.gridliner import LongitudeFormatter, LatitudeFormatter
+
+import geocat.viz as gv
+
+###############################################################################
+# Plot
+
+# Generate a figure and axes
+plt.figure(figsize=(12, 10))
+
+# Define axis using Cartopy
+projection = ccrs.PlateCarree()
+ax = plt.axes(projection=projection)
+
+# Add coastlines to plot
+ax.coastlines()
+
+# Define latitude and longitudes for the markers
+lat = np.arange(-70, 85, 20)
+lon = np.arange(-160, 170, 20)
+
+# Make a meshgrid of the latitudes and longitudes
+lons, lats = np.meshgrid(lon, lat)
+
+# Randomly remove some of the points from the meshgrid
+mask = np.random.rand(lats.shape[0], lats.shape[1]) < 0.35
+lats = lats[~mask]
+lons = lons[~mask]
+
+# Create an array of colors to choose from
+colors = ['blue', 'green', 'red', 'yellow', 'purple']
+
+# Create a scatter plot of the latitudes and longitudes with a random color
+# from the colors array and a square marker to imitate a grid of colors
+ax.scatter(
+    lons,
+    lats,
+    c=[colors[i] for i in np.random.randint(0, len(colors), size=lats.size)],
+    edgecolors='face',
+    s=1350,
+    alpha=0.75,
+    zorder=2,
+    marker='s')
+
+# Use geocat-viz utility function to format latitude/longitude labels
+gv.add_lat_lon_ticklabels(ax)
+
+# Remove degree symbol from tick labels
+ax.yaxis.set_major_formatter(LatitudeFormatter(degree_symbol=''))
+ax.xaxis.set_major_formatter(LongitudeFormatter(degree_symbol=''))
+
+# Use geocat-viz utility function to format major and minor tick marks
+gv.add_major_minor_ticks(ax, labelsize=14)
+
+# Use geocat-viz utility function to format tick labels
+gv.set_axes_limits_and_ticks(ax=ax,
+                             xlim=(-180, 181),
+                             ylim=(-90, 91),
+                             xticks=np.arange(-180, 190, 30),
+                             yticks=np.arange(-90, 100, 30))
+
+# Add title
+plt.title('Dummy markers over a map', fontweight='bold', fontsize=20, pad=20)
+
+# Show the plot
+plt.show()