Parse Raw NDBC Directional Wave Spectra

buoyspectraplotter.py

import urllib.request as request
import json
import matplotlib.pyplot as plt
import matplotlib.colors as colors
import matplotlib.cm as cm
import numpy as np

class BuoySpectraPlotter:

    def __init__(self, buoy_station):
        self.data = None
        self.buoy_station = buoy_station

    def fetch_data(self):
        url = 'https://buoyfinder.appspot.com/api/latest/wave/' + self.buoy_station
        req = request.Request(url)
        with request.urlopen(req) as response:
            self.data = json.loads(response.read().decode('utf8'))

        return self.data is not None

    def plot_radar(self):
        if self.data is None:
            return

        frequencies = np.array(self.data['BuoyData']['WaveSpectra']['Frequencies'])
        energies = np.array(self.data['BuoyData']['WaveSpectra']['Energies'])
        angles = np.array(self.data['BuoyData']['WaveSpectra']['Angles']) * (np.pi/180.0)

        ax = plt.subplot(111, projection='polar')
        ax.set_title('Station ' + self.buoy_station + ': Directional Wave Spectra\n')
        ax.set_theta_zero_location('N')
        ax.set_theta_direction(-1)
        bars = ax.bar(angles, energies, align='center')

        # Map the color of each bar in the plot to its period value
        norm = colors.Normalize(vmin=frequencies[0], vmax=frequencies[-1])
        cmap = cm.jet_r
        colormap = cm.ScalarMappable(norm=norm, cmap=cmap)
        for freq, energy, bar in zip(frequencies, energies, bars):
            bar.set_facecolor(colormap.to_rgba(freq))
            bar.set_alpha(0.5)

        plt.show()

if __name__ == '__main__':
    buoy_plotter = BuoySpectraPlotter('44097')
    buoy_plotter.fetch_data()
    buoy_plotter.plot_radar()