>>> """
================
Parasite Simple2
================

"""
... import matplotlib.transforms as mtransforms
... import matplotlib.pyplot as plt
... from mpl_toolkits.axes_grid1.parasite_axes import HostAxes
... 
... obs = [["01_S1", 3.88, 0.14, 1970, 63],
...        ["01_S4", 5.6, 0.82, 1622, 150],
...        ["02_S1", 2.4, 0.54, 1570, 40],
...        ["03_S1", 4.1, 0.62, 2380, 170]]
... 
... 
... fig = plt.figure()
... 
... ax_kms = fig.add_subplot(axes_class=HostAxes, aspect=1)
... 
... # angular proper motion("/yr) to linear velocity(km/s) at distance=2.3kpc
... pm_to_kms = 1./206265.*2300*3.085e18/3.15e7/1.e5
... 
... aux_trans = mtransforms.Affine2D().scale(pm_to_kms, 1.)
... ax_pm = ax_kms.twin(aux_trans)
... 
... for n, ds, dse, w, we in obs:
...     time = ((2007 + (10. + 4/30.)/12) - 1988.5)
...     v = ds / time * pm_to_kms
...     ve = dse / time * pm_to_kms
...     ax_kms.errorbar([v], [w], xerr=[ve], yerr=[we], color="k")
... 
... 
... ax_kms.axis["bottom"].set_label("Linear velocity at 2.3 kpc [km/s]")
... ax_kms.axis["left"].set_label("FWHM [km/s]")
... ax_pm.axis["top"].set_label(r"Proper Motion [$''$/yr]")
... ax_pm.axis["top"].label.set_visible(True)
... ax_pm.axis["right"].major_ticklabels.set_visible(False)
... 
... ax_kms.set_xlim(950, 3700)
... ax_kms.set_ylim(950, 3100)
... # xlim and ylim of ax_pms will be automatically adjusted.
... 
... plt.show()
...