from mathutils import *
from plotutils import *
        

x = [ 11.0, 12.0, 13.0, 14.0, 15.0, 16.0,  17.0,18.0]
y = [ 30.0, 22.0, 12.0, 10.0, 11.0, 14.0, 21.0, 32.0]
v = [  0.3,  0.8,  0.4,  0.3,  0.5,  0.4,  0.3,  0.2]

w = [ 1/ max(i,0.1) for i in v]



p=plot(None)[0]
p.setStyle(p.Style.ErrorY)
p.setLegendVisible(True)
s1 = LinePlotErrorSeries("Observed Data")
p.addSeries(s1)
for i in range(len(x)):\
    s1.appendData(x[i], y[i], v[i])
    
    
pars_polynomial=  fit_polynomial(y, x, 2, None, w)
function = PolynomialFunction(pars_polynomial)
plot_function(p, function, "Fit" , frange (min(x), max(x), 0.1), False)

print "(a0,a1,a2) = " , pars_polynomial

for xp in x:
    print xp, poly(xp, pars_polynomial)