# -*- coding: utf-8 -*-
"""
Created on Wed Sep 20 08:52:00 2017

@author: Miguel Almeida
"""

import numpy
import matplotlib.pyplot as plt

def load_planet_data(file_name):
    """Return matrix with orbital radius and period"""
    rows = []
    lines = open(file_name).readlines()
    
    for line in lines[1:]:
        parts = line.split(',')
        rows.append( (float(parts[1]), float(parts[2])))
        
    return numpy.array(rows)

data = load_planet_data('planets.csv')



def data_as_si(planet_data):
    #converts the planet data from AU and years to SI units
    
    AU_METERS = 1.496e11
    YEAR_SECONDS = 3.16e7
    
    si_radii= planet_data[:,0]*AU_METERS
    si_periods = planet_data[:,1]*YEAR_SECONDS
    
    return si_radii, si_periods

def star_mass(filename):
    G = 6.67e-11
    
    radii, periods = data_as_si(load_planet_data(filename))
    
    velocities = 2*numpy.pi*radii/periods
    
    masses = velocities**2 * radii/G
    
    return numpy.mean(masses), numpy.std(masses)

print(star_mass('planets.csv'))
    
    
    
    data = load_planet_data('planets.csv')

    x = data[:,0]
    y = data[:,1]
    
    coefs = numpy.polyfit(x,y,2)
    pxs = numpy.linespace(0,max(x),100)
    poly = numpy.polyval(coefs, pxs)
    
    import matplotlib.pyplot as plt
plt.figure()
plt.plot(data[:,0],data[:,1])
plt.show()
plt.close()