Untitled

How to change offsets of matplotlib LineCollection after creation
import matplotlib.pyplot as plt
import matplotlib.collections
import numpy as np

x=np.arange(1000)
y=np.sin(x/50.)
l=zip(x,y)

f=plt.figure()
a=f.add_subplot(111)
lines=matplotlib.collections.LineCollection((l,l), offsets=(0,0.2))
a.add_collection(lines)
a.autoscale_view(True, True, True)
plt.show()

a.collections[0].set_offsets((0, 0.5))

lines.set_offsets( (0., 0.2))
lines.set_segments( (l,l) )

lines._paths[1].vertices[:,1] += 1

def set_offsets(newoffsets, ax=None, c_num=0):
    '''
        Modifies the offsets between curves of a LineCollection

    '''

    if ax is None:
        ax=plt.gca()

    lcoll=ax.collections[c_num]
    oldoffsets=lcoll.get_offsets()

    if len(newoffsets)==1:
        newoffsets=[i*np.array(newoffsets[0]) for
         (i,j) in enumerate(lcoll.get_paths())]
    if len(oldoffsets)==1:
        oldoffsets=[i*oldoffsets[0] for (i,j) in enumerate(newoffsets)]

    verts=[path.vertices for path in lcoll.get_paths()]

    for (oset, nset, vert) in zip(oldoffsets, newoffsets, verts):
        vert[:,0]+=(-oset[0]+nset[0])
        vert[:,1]+=(-oset[1]+nset[1])

    lcoll.set_offsets(newoffsets)
    lcoll.set_paths(verts)