#!/usr/bin/env python3
# -*- coding: utf-8 -*-
"""
Created on Wed Jun 21 12:21:29 2023

@author: richardson
"""

import numpy as np # numpy is a numerical package
import matplotlib.pyplot as plt
# matplotlib is a plotting package, and 
# pyplot is one of the subpackages

x = np.linspace(-np.pi,np.pi,100)
# this makes a list (actually np array)
# of the numbers between -pi and pi --- 100 of them
# print(x)
a = plt.plot(x,20*np.cos(x),color='red')
xx = np.random.randn(20)
# randn(N) chooses N random numbers 
# according to the normal distribution
# it makes a list (actually an np array)
yy = xx**2-xx-10+np.random.rand(20)*40
# xx**2 means the np array where each element
# of xx is squared.
# Except for the random part, it is evaluating
# y = x**2 - x-10 --- just for those 20 points
# rand(N) is N random numbers between 0 and 1
# (according to a uniform distribution)
# 40*rand(N) means N random numbers between 0 and 40.
b =plt.scatter(xx,yy,color="blue",marker="v")
# choose markers here:
# https://matplotlib.org/stable/api/markers_api.html#module-matplotlib.markers
# this will make a scatter plot
z=np.zeros(100)
# vector of 100 zeros (i.e. np array of zeros)
plt.plot(x,z,color="black")
plt.show()