Earthquakes plotting solution (2021-2022)

plot_earthquakes.py

"""A sample answer to https://github.com/UCL-MPHY0021-21-22/RSE-Classwork/issues/15."""

import json
import statistics
from datetime import date

import matplotlib.pyplot as plt
import requests


def get_data():
    """Retrieve the data we will be working with."""
    response = requests.get(
        "http://earthquake.usgs.gov/fdsnws/event/1/query.geojson",
        params={
            'starttime': "2000-01-01",
            "maxlatitude": "58.723",
            "minlatitude": "50.008",
            "maxlongitude": "1.67",
            "minlongitude": "-9.756",
            "minmagnitude": "1",
            "endtime": "2018-10-11",
            "orderby": "time-asc"}
    )
    text = response.text
    return json.loads(text)


def get_year(earthquake):
    """Extract the year in which an earthquake happened."""
    timestamp = earthquake['properties']['time']
    year = date.fromtimestamp(timestamp/1000).year
    return year


def get_magnitude(earthquake):
    """Retrive the magnitude of an earthquake item."""
    return earthquake["properties"]["mag"]


def plot_average_magnitude_per_year(earthquakes):
    magnitudes_per_year = get_magnitudes_per_year(earthquakes)
    # Convert to lists for plotting
    # Note that we have to ensure the same ordering in both lists!
    # This is one way:
    years = sorted(magnitudes_per_year.keys())
    magnitudes = [
        # the statistics module has some basic statistical functions
        statistics.mean(magnitudes_per_year[year])
        for year in years
    ]
    plt.plot(years, magnitudes)
    plt.xlabel("Year")
    plt.ylabel("Magnitude")
    plt.title("Average earthquake magnitude per year")
    plt.savefig("average_magnitudes.png")


def plot_number_per_year(earthquakes):
    magnitudes_per_year = get_magnitudes_per_year(earthquakes)
    # Convert to lists for plotting
    # Note that we have to ensure the same ordering in both lists!
    # This is one way:
    years = sorted(magnitudes_per_year.keys())
    numbers = [len(magnitudes_per_year[year]) for year in years]
    plt.bar(years, numbers)
    plt.xlabel("Year")
    plt.ylabel("Count")
    plt.title("Number of earthquakes per year")
    plt.savefig("frequencies.png")  # Save the figure to a file


def get_magnitudes_per_year(earthquakes):
    """Retrieve the magnitudes of all the earthquakes in a given year.
    
    Returns a dictionary with years as keys, and lists of magnitudes as values.
    """
    magnitudes_per_year = {}
    for earthquake in earthquakes:
        year = get_year(earthquake)
        magnitude = get_magnitude(earthquake)
        if year not in magnitudes_per_year:  # if we haven't seen this year before, add it
            magnitudes_per_year[year] = [magnitude]
        else:  # otherwise record one more instance
            magnitudes_per_year[year].append(magnitude)
    return magnitudes_per_year

# Get the data we will work with
quakes = get_data()['features']

# Plot the results - this is not perfect since the x axis is shown as real
# numbers rather than integers, which is what we would prefer!
plot_number_per_year(quakes)
plt.clf()  # This clears the figure, so that we don't overlay the two plots
plot_average_magnitude_per_year(quakes)