make use of plotter.bands in tutorial

doc/source/images/band_structure.py.diff

 --- original
 +++ modified
-@@ -12,6 +12,7 @@
+@@ -10,6 +10,7 @@
  
- # For plotting
+ # For plotting.
  from matplotlib import pyplot
 +import _defs
  
- 
  def make_lead(a=1, t=1.0, W=10):
-@@ -38,11 +39,19 @@
-     bands = kwant.physics.Bands(lead)
-     energies = [bands(k) for k in momenta]
+     # Start with an empty lead with a single square lattice
+@@ -33,10 +34,19 @@
  
--    pyplot.figure()
-+    fig = pyplot.figure()
-     pyplot.plot(momenta, energies)
--    pyplot.xlabel("momentum [in units of (lattice constant)^-1]")
--    pyplot.ylabel("energy [in units of t]")
+ def main():
+     lead = make_lead().finalized()
+-    kwant.plotter.bands(lead, show=False)
+-    pyplot.xlabel("momentum in units of inverse lattice constant")
+-    pyplot.ylabel("energy in units of t")
 -    pyplot.show()
-+    pyplot.xlabel("momentum [in units of (lattice constant)^-1]",
++    fig = kwant.plotter.bands(lead, show=False)
++    pyplot.xlabel("momentum in units of inverse lattice constant",
 +                 fontsize=_defs.mpl_label_size)
-+    pyplot.ylabel("energy [in units of t]", fontsize=_defs.mpl_label_size)
++    pyplot.ylabel("energy in units of t", fontsize=_defs.mpl_label_size)
 +    pyplot.setp(fig.get_axes()[0].get_xticklabels(),
 +               fontsize=_defs.mpl_tick_size)
 +    pyplot.setp(fig.get_axes()[0].get_yticklabels(),
@@ -29,6 +28,7 @@
 +    fig.subplots_adjust(left=0.15, right=0.95, top=0.95, bottom=0.15)
 +    fig.savefig("band_structure_result.pdf")
 +    fig.savefig("band_structure_result.png", dpi=_defs.dpi)
++
  
  
- def main():
+ # Call the main function if the script gets executed (as opposed to imported).

doc/source/images/superconductor_band_structure.py.diff

@@ -8,13 +8,13 @@
  
  tau_x = tinyarray.array([[0, 1], [1, 0]])
  tau_z = tinyarray.array([[1, 0], [0, -1]])
-@@ -46,12 +47,19 @@
-     bands = kwant.physics.Bands(lead)
-     energies = [bands(k) for k in momenta]
+@@ -46,11 +47,19 @@
+     # Make system and finalize it right away.
+     lead = make_lead().finalized()
  
--    pyplot.figure()
-+    fig = pyplot.figure()
-     pyplot.plot(momenta, energies)
+-    kwant.plotter.bands(lead, momenta=np.linspace(-1.5, 1.5, 101), show=False)
++    fig = kwant.plotter.bands(lead, momenta=np.linspace(-1.5, 1.5, 101),
++                              show=False)
      pyplot.xlabel("momentum [in untis of (lattice constant)^-1]")
      pyplot.ylabel("energy [in units of t]")
      pyplot.ylim([-0.8, 0.8])
@@ -29,4 +29,4 @@
 +    fig.savefig("superconductor_band_structure_result.png", dpi=_defs.dpi)
  
  
- def main():
+ # Call the main function if the script gets executed (as opposed to imported).

doc/source/reference/kwant.plotter.rst

@@ -11,6 +11,7 @@ Plotting routine
 
    plot
    map
+   bands
 
 Data-generating functions
 -------------------------

doc/source/tutorial/band_structure.py

@@ -8,12 +8,9 @@
 
 import kwant
 
-from math import pi
-
-# For plotting
+# For plotting.
 from matplotlib import pyplot
 
-
 #HIDDEN_BEGIN_zxip
 def make_lead(a=1, t=1.0, W=10):
     # Start with an empty lead with a single square lattice
@@ -37,24 +34,12 @@ def make_lead(a=1, t=1.0, W=10):
 
 
 #HIDDEN_BEGIN_pejz
-def plot_bandstructure(lead, momenta):
-    bands = kwant.physics.Bands(lead)
-    energies = [bands(k) for k in momenta]
-
-    pyplot.figure()
-    pyplot.plot(momenta, energies)
-    pyplot.xlabel("momentum [in units of (lattice constant)^-1]")
-    pyplot.ylabel("energy [in units of t]")
-    pyplot.show()
-
-
 def main():
     lead = make_lead().finalized()
-
-    # list of momenta at which the bands should be computed
-    momenta = [-pi + 0.02 * pi * i for i in xrange(101)]
-
-    plot_bandstructure(lead, momenta)
+    kwant.plotter.bands(lead, show=False)
+    pyplot.xlabel("momentum in units of inverse lattice constant")
+    pyplot.ylabel("energy in units of t")
+    pyplot.show()
 #HIDDEN_END_pejz
 
 

doc/source/tutorial/superconductor_band_structure.py

@@ -44,28 +44,17 @@ def make_lead(a=1, t=1.0, mu=0.7, Delta=0.1, W=10):
 #HIDDEN_END_nbvn
 
 
-def plot_bandstructure(lead, momenta):
-    bands = kwant.physics.Bands(lead)
-    energies = [bands(k) for k in momenta]
+def main():
+    # Make system and finalize it right away.
+    lead = make_lead().finalized()
 
-    pyplot.figure()
-    pyplot.plot(momenta, energies)
+    kwant.plotter.bands(lead, momenta=np.linspace(-1.5, 1.5, 101), show=False)
     pyplot.xlabel("momentum [in untis of (lattice constant)^-1]")
     pyplot.ylabel("energy [in units of t]")
     pyplot.ylim([-0.8, 0.8])
     pyplot.show()
 
 
-def main():
-    # Make system and finalize it right away.
-    lead = make_lead().finalized()
-
-    # list of momenta at which the bands should be computed
-    momenta = np.linspace(-1.5, 1.5, 201)
-
-    plot_bandstructure(lead, momenta)
-
-
 # Call the main function if the script gets executed (as opposed to imported).
 # See <http://docs.python.org/library/__main__.html>.
 if __name__ == '__main__':

doc/source/tutorial/tutorial3.rst

@@ -31,11 +31,11 @@ contained implicitly finalized versions of the attached leads.  But now we are
 working with a single lead and there is no scattering region.  So we have to
 finalized the ``Builder`` of our sole lead explicitly.
 
-That finalized lead is then passed to `kwant.physics.Bands`.  This
-creates an object that behaves just like a function: when called with a
-momentum ``k`` as parameter it returns the eigenenergies of the translational
-invariant system for that momentum.  Computing these eigenenergies for a range
-of momenta then yields the bandstructure:
+That finalized lead is then passed to `~kwant.plotter.bands`.  This function
+calculates energies of various bands at a range of momenta and plots the
+calculated energies. It is really a convenience function, and if one needs to
+do something more profound with the dispersion relation these energies may be
+calculated directly. For now we just plot the bandstructure:
 
 .. literalinclude:: band_structure.py
     :start-after: #HIDDEN_BEGIN_pejz