# test_polyfit.py     polyfit in Python, needs numpy
from numpy import array
from numpy import polyfit
from numpy import polyval
import pylab

print "test_polyfit.py  a x,y,5) "

x=array([0.0, 0.1,  0.2, 0.3, 0.4, 1.8, 1.9])
print "x="
print  x
y=array([0.0, 6.0, 14.1, 5.5, 4.5, 4.5, 0.0])
print "y="
print y

p=polyfit(x,y,5)
print "polyfit p=polyfit(x,y,5)"
print p

# polyval
y1=polyval(p,x)
print "polyval y1=polyval(p,x)"
print y1

err=abs(y-y1)
print "err=abs(y-y1) an array",
print err

sumerr=sum(err)
print "sumerr=sum(err) a number",
print sumerr

print "generating plot test_polyfit_py.png"
pylab.plot(x, y)
pylab.xlabel("time")
pylab.ylabel("thrust")
pylab.grid(True)
pylab.title("thrust data plotting by python")
pylab.savefig("test_polyfit_py") # writes .png
pylab.show()

pylab.plot(x, y1)
pylab.title("the polyfit")
pylab.savefig("test_polyfit2_py") # writes .png
pylab.show()