Fix taxi example [ci skip]

Author: astrofrog

examples/convert_nyc.py

@@ -1,8 +1,8 @@
-import os
 import sys
 
 import numpy as np
 
+import pandas
 import matplotlib.pyplot as plt
 
 # The following is needed to register the axes
@@ -11,26 +11,35 @@
 from astropy.visualization import LogStretch
 from astropy.visualization.mpl_normalize import ImageNormalize
 
-norm = ImageNormalize(vmin=0., vmax=1000, stretch=LogStretch())
+if len(sys.argv) != 2:
+    print("Example usage: python example_taxi.py yellow_tripdata_2016-05.csv")
+    print("You can get the data at: http://www.nyc.gov/html/tlc/html/about/trip_record_data.shtml")
+    sys.exit(1)
 
-ax = plt.subplot(1, 1, 1, aspect='equal', projection='scatter_density')
+filename = sys.argv[1]
 
-xmin = -8240227.037
-ymin = 4974203.152
-xmax = -8231283.905
-ymax = 4979238.441
+print("Reading file (this typically takes 10-20 seconds)...")
+df = pandas.read_csv(filename, usecols=['dropoff_longitude', 'dropoff_latitude']).dropna(axis=0)
+x = df['dropoff_longitude']
+y = df['dropoff_latitude']
 
-if not os.path.exists('taxi.npz'):
-    print("You need to run the convert_nyc.py script first")
-    sys.exit(1)
+print("Done reading file, making plot")
+
+norm = ImageNormalize(vmin=0., vmax=1000, stretch=LogStretch())
+
+ax = plt.subplot(1, 1, 1, projection='scatter_density')
+
+xmin = -74.15
+xmax = -73.75
+ymin = 40.62
+ymax = 40.85
 
-arrays = np.load('taxi.npz')
-x = arrays['x']
-y = arrays['y']
+aspect = 1 / np.cos(np.radians(0.5 * (ymin + ymax)))
 
-ax.rasterized_scatter(x, y, colormap='plasma', norm=norm)
+ax.scatter_density(x, y, cmap='plasma', norm=norm)
 ax.set_xlim(xmin, xmax)
 ax.set_ylim(ymin, ymax)
-ax.set_aspect('equal')
+ax.set_xlabel
+ax.set_aspect(aspect)
 
 plt.show()