"""
Exercise 5.18 from " A primer on..."
Read data from file and plot it. Read data and use numpy
tools to fit polynomials to the data. We import the
function from exercise 5.16 and use it to read the data from file
"""


import numpy as np
import matplotlib.pyplot as plt
import sys
from read_density_data import read_density_data

#a)
def fit(x, y, deg):
    for d in deg:
        coeff = np.polyfit(x, y, d)
        p = np.poly1d(coeff)
        y_fitted = p(x)
        plt.plot(x, y_fitted, label=f'Degree {d}')
    plt.plot(x, y, 'ro', label = 'Data')
    plt.legend()
    plt.show()

#b)
if __name__ == "__main__":
    filename = sys.argv[1]
    temp, dens = read_density_data(filename)
    fit(temp, dens, [1,2])