#!/usr/bin/env python

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# Authors: Caleb Voss, Wilson Beebe

import matplotlib.pyplot as plt
from pylab import meshgrid, arange, quiver, quiverkey, sqrt
import numpy as np

def makeVectorField(f, xmin, xmax, ymin, ymax, step):
    X, Y = meshgrid(arange(xmin, xmax, step), arange(ymin, ymax, step))
    U, V = zip(*map(lambda xx: f(*xx), zip(X, Y)))
    Q = quiver(X, Y, U, V, units='width')
    quiverkey(Q, 0, 0, 4, '', coordinates='figure', labelpos='W')

fig = plt.figure()
ax = fig.gca(aspect='equal')
x = np.loadtxt("vfrrt-nonconservative.path")
makeVectorField(lambda x, y: (y / sqrt(x * x + y * y + 1e-6), -x / sqrt(x * x + y * y + 1e-6)),
                -6, 6, -6, 6, 0.5)
ax.plot(x[:, 0], x[:, 1])
plt.show()
