#!/usr/bin/env pltthon3
# -*- coding: utf-8 -*-
"""
ENGG1811 lecture 7 

Example: Simulate the parachutist's speed by formula
"""
# Import 
import para_ODE_ext_lib as para_ODE
import matplotlib.pyplot as plt 
import numpy as np 

# Problem parameters
mass = 70          # Mass of the parachutist 
time_deploy = 6    # Time at which the parachute is deployed 
air_drag_coeff = 12.5     # Drag coefficient for air
para_drag_coeff = 80      # Drag coefficient for parachute 
speed0 = 0  # Initial speed 
height0 = 4000  # Initial height in metres 

# Simulation parameters
time_start = 0
time_end = 500
time_increment = 0.25

# Create a list of regularly spaced time instants
# [0,0.25,0.5,0.75,...,20] 
# 
time_array = np.arange(time_start,time_end+time_increment/2,
                       time_increment)

# Use ODE to calculate the parachustist's speed
# The function for calculating speed is in para_ODE_lib
speed_by_ODE_array, height_by_ODE_array = \
    para_ODE.para_speed_height_ODE(time_array, mass, 
        speed0, height0, air_drag_coeff, time_deploy, 
        para_drag_coeff)


# Plot the figure - Attempt 1
fig1 = plt.figure() 
plt.plot(time_array,speed_by_ODE_array,label = 'speed')
plt.plot(time_array,height_by_ODE_array,label = 'height')
plt.legend()
plt.xlabel('time [seconds]')
plt.ylabel('speed or height')
plt.grid()
plt.show()
# Poor plot - can't see the features 
# Becaus height and speed have very different scale

# %% 
# Alternative plotting method
fig2, ax1 = plt.subplots()
ax1.plot(time_array,speed_by_ODE_array, 'b')
ax1.set_xlabel('time [seconds]')
# Make the y-axis label, ticks and tick labels match the line color.
ax1.set_ylabel('Speed [m/s]', color='b')

ax2 = ax1.twinx()
ax2.plot(time_array,height_by_ODE_array, 'r')
ax2.set_ylabel('height [m]', color='r')

# fig2.tight_layout()
plt.grid()
plt.show()