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#!/usr/bin/env python

# Exercise (b)

import pylab as n
import numpy.random as r
import sys
import os

def generate (seq_0, start, stop,save=False):
    x = n.linspace ( start, stop, 100 )
    y = n.poly1d ( seq_0 )
    e = r.random_integers ( -250, 250, size=(100) ) * 1e-2
    if save:
        file = open ( 'xy-points.txt', 'w' )
        for i in range ( 100 ):
            file.write ( '%f\t%f\n' % ( x[i], y(x[i]) + e[i] ) )
        file.close()
    else:
        return (x, y(x)+e)

def fit_from_file():
    file = open ( 'xy-points.txt', 'r' )
    x, y = [], []
    lines = file.readlines()
    file.close()
    for line in lines:
        line = line.split()
        x.append ( float ( line[0] ) )
        y.append ( float ( line[1] ) )
    fit_curve = n.polyfit ( x, y, 2 )
    fit_curve = n.poly1d ( fit_curve )
    return x, y, fit_curve(x)

def fit(x,y):
    fit_curve = n.polyfit ( x, y, 2 )
    fit_curve = n.poly1d ( fit_curve )
    return fit_curve(x)

def plotten ( x, y, fit ):
    
    lines = n.plot ( x, y, 'ro', x, fit, 'g:', lw = 3 )
    patch = []
    a,b = n.argmin(abs(x)), n.argmin(abs(x-n.pi/3.))
    F = fit.copy()
    F[:a] = 0
    F[b:] = 0
    
    n.fill_between(x,fit,y2=0,where=F,alpha=.5,facecolor='c')
    n.legend ( [lines], ( 'Datenpunkte', 'Fitkurve' ) )
    n.show()

if __name__ == '__main__':
    usage_string = """Usage: ./aufg3_2.py -<option>
Values for <option>:
'no-gen <filename>' Do no generate data"""

    x,y = None, None

    if len(sys.argv) > 1:
        if '-no-gen' in sys.argv:
            i = sys.argv.index('-no-gen')
            if os.path.isfile(sys.argv[i+1]):
                x,y,f = fit_from_file()
    
    if not (x and y):
        x,y = generate((2,-4,3),-1,5)
        f = fit(x,y)
        
    plotten(x,y,f)