# -*- coding: utf-8 -*-
"""
Created on Sun Nov 06 08:49:00 2016

@author: wderousse
"""

import sys
import xlrd
import numpy as np
import matplotlib.pyplot as plt
from scipy.interpolate import interp1d

np.set_printoptions(threshold=np.nan)
print sys.version
print __name__

filename='linear_2.xlsx'
print
print 'Opening',filename
ss=xlrd.open_workbook(filename,on_demand=True)
sheet_index=0
print ' Worksheet',ss.sheet_names()[sheet_index]
sh=ss.sheet_by_index(sheet_index)

print ' Reading data values'
xa=[]
ya=[]
for row_index in range(0,sh.nrows):
    xa.append(sh.cell_value(row_index,0))
    ya.append(sh.cell_value(row_index,1))
xa=np.array(xa)
ya=np.array(ya)
print ' Design x array size:',len(xa)
print ' Design y array size:',len(ya)


coeff=np.polyfit(xa, ya, 3, 0.0, 'true')
print
print coeff

print
p=np.poly1d(coeff[0])
print p(-10)
print
print p

plt.axis([-10,10,-50,50])
plt.plot(xa,ya,'ro')
x=np.arange(-10,10,0.1)
y=np.array(-0.1020*x**3-0.1178*x**2+0.2065*x+3.063)
plt.plot(x,y)