7.1. Railway Statistics 2

In this question, you will analyze some railway statistics regarding the length of all railroads and the number of passengers year by year in Turkey.

You can fetch this data from the following link:

http://user.ceng.metu.edu.tr/~ceng240/data/railway.csv

Here are the instructions of the task:

  • Read this data by using \(\color{purple}{\texttt{pandas}}\) module.

  • Get the lengths of railroads, in a \(\color{purple}{\texttt{numpy}}\) array with dtype as int from the field named Length.

  • Get the number of passengers, in a \(\color{purple}{\texttt{numpy}}\) array with dtype as int from the field named Passenger.

  • Plot the figure for the lengths of railroads vs. the number of passengers by using \(\color{purple}{\texttt{matplotlib.pyplot}}\) and save in your computer (see \(\color{purple}{\texttt{savefig()}}\) function in the related module.).

  • Apply min max normalization to both fields. During this normalization each value in the fields is calculated according to the formula below:

    (7.1.1)\[new\_value = \frac{value - min\_value}{max\_value - min\_value}\]

  • Plot the figure for the lengths of railroads vs. the number of passengers by using \(\color{purple}{\texttt{matplotlib.pyplot}}\) with their normalized values again and save in your computer.

Write a python program to complete tasks above. You are recommended to define a function in case of a repeating task.

import pandas as pd
import numpy as np
import matplotlib.pyplot as plt

# function that applies min max normalization to given numpy array
def min_max_normalization(arr):
    min_value = arr.min()
    max_value = arr.max()

    return (arr - min_value) / (max_value - min_value)

# function that plots and saves the figure with given data, title and output path
def plot_data(x, y, title, output_path):
    plt.figure()
    plt.plot(x, y)
    plt.title(title)
    plt.savefig(output_path)

raw_data = pd.read_csv("railway.csv")

lengths = np.array(raw_data["Length"], dtype=int)
passengers = np.array(raw_data["Passenger"], dtype=int)

normalized_lengths = min_max_normalization(lengths)
normalized_passengers = min_max_normalization(passengers)

plot_data(lengths, passengers, "RAW", "railway_raw.png")
plot_data(normalized_lengths, normalized_passengers, "NORMALIZED", "railway_normalized.png")