import holoviews as hv
from holoviews import opts

hv.extension('matplotlib')

# build a dataset where multiple columns measure the same thing
stamp    = [.33, .33, .34, .37, .37, .37, .37, .39, .41, .42,
            .44, .44, .44, .45, .46, .49, .49]
postcard = [.20, .20, .21, .23, .23, .23, .23, .24, .26, .27,
            .28, .28, .29, .32, .33, .34, .35]

group = "U.S. Postage Rates (1999-2015)"
stamp    = hv.Curve(stamp, vdims='Rate per ounce', label='stamp', group=group)
postcard = hv.Curve(postcard, vdims='Rate per ounce', label='postcard', group=group)
postage = (stamp * postcard)

postage.opts(
    opts.Curve(interpolation='steps-mid', linestyle=hv.Cycle(values=['--', '-'])),
    opts.Overlay(legend_position='top_left'))