I remember plotting straight lines from Algebra Class.
""" class03p11.py This script should use Pandas to plot prices of GSPC for 2016. This script should Plot a straight line from first price to last price. """ import pandas as pd import matplotlib.pyplot as plt csvfile = 'http://spy611.herokuapp.com/csv/allpredictions.csv' cp_df = pd.read_csv(csvfile).sort_values(['cdate']) cp2016_sr = (cp_df.cdate > '2016') & (cp_df.cdate < '2017') cp2016_df = cp_df[['cdate','cp']][cp2016_sr] # Algebra and Geometry say a line is described by # y = mx + b # m, the slope is (y1-y0)/(x1-x0): # Useful concept: # If I use integers (starting at 0) as X-values, # then my syntax is simpler. # (x1-x0) is: x1x0_i = len(cp2016_df) # (y1-y0) is: y1y0_f = cp2016_df.iloc[-1].cp-cp2016_df.iloc.cp # m, the slope is (y1-y0)/(x1-x0): m_f = y1y0_f / x1x0_i # And b is the y intercept: b_f = cp2016_df.iloc.cp # My equation for straight line: def yval(x_in): return m_f * x_in + b_f # I should collect points to plot straight line: yvals_l = [ yval(x_i) for x_i in range(len(cp2016_df))] # Add the points to the DataFrame: cp2016_df['sl'] = yvals_l # To make a better plot I should convert X-values from integers to series of strings: cpdate2016_df = cp2016_df.set_index(['cdate']) # I should plot cp (closing price), and straight line: cpdate2016_df.plot.line(title="GSPC 2016") plt.show() 'bye'