# paste this code at the end of VectorFieldPlot 1.0
doc = FieldplotDocument('VFPt_decapole_wires', width=600, height=600, commons=True)
nw = 10
r = 2.0
wires = []
for i in range(nw):
    wires.append([r * cos(2*pi*i/float(nw)),
                  r * sin(2*pi*i/float(nw)),
                  2 * (i % 2) - 1])
field = Field({'wires':wires})
doc.draw_currents(field)

t0 = 0.085
Fsum = ig.quad(lambda t: sc.dot(field.F([t,0]), [0,1]), 0.0, r*(1-t0))[0]

nl = 8
for i in range(nl):
    a = (i + 0.5) / (nl - 0.5)
    t1 = op.brentq(lambda t1: ig.quad(lambda t:
        sc.dot(field.F([t,0]), [0,1]), 0.0, t1)[0] - a * Fsum, 0.0, r*(1-t0))
    if i in [0, 2, 4, 6]: offs = 0.0
    else: offs = 0.5
    for m in range(nw):
        c, s = cos(2*pi*m/float(nw)), sin(2*pi*m/float(nw))
        line = FieldLine(field, [t1*c, t1*s], directions='both')
        doc.draw_line(line, arrows_style={'dist':1.7,
            'offsets':[offs, 0.4, 0.4, 1.0-offs]})
doc.write()