diff --git a/doc/source/images/band_structure.py.diff b/doc/source/images/band_structure.py.diff
index a7585168982f4a2008e5215ed2742843b0137cf3..3b72444cdc6043c7e26445f6b4d376c0fcc093b2 100644
--- a/doc/source/images/band_structure.py.diff
+++ b/doc/source/images/band_structure.py.diff
@@ -1,26 +1,25 @@
--- 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).
diff --git a/doc/source/images/superconductor_band_structure.py.diff b/doc/source/images/superconductor_band_structure.py.diff
index 8fa888ba89672bb0a32c013e31f0b7a097fe8604..2590026c9a158c70f547e974ea25087763d5ce89 100644
--- a/doc/source/images/superconductor_band_structure.py.diff
+++ b/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).
diff --git a/doc/source/reference/kwant.plotter.rst b/doc/source/reference/kwant.plotter.rst
index 0ffcae77e9671cd446aa4664ffbc4c6e9dec2cae..729d9fc0c606463c81aa88a60887b03e8bc8ad72 100644
--- a/doc/source/reference/kwant.plotter.rst
+++ b/doc/source/reference/kwant.plotter.rst
@@ -11,6 +11,7 @@ Plotting routine
plot
map
+ bands
Data-generating functions
-------------------------
diff --git a/doc/source/tutorial/band_structure.py b/doc/source/tutorial/band_structure.py
index 012d14fbbaed0ba03d461efa4d18bf415c98d111..2ad2e3dbe22e3713e814a36cad0abcd039701802 100644
--- a/doc/source/tutorial/band_structure.py
+++ b/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
diff --git a/doc/source/tutorial/superconductor_band_structure.py b/doc/source/tutorial/superconductor_band_structure.py
index 816c32f163f512950e7912e9b9a207d0a586971e..6bed20b2d61809813bad9c5f9fb5b93f636b6f8f 100644
--- a/doc/source/tutorial/superconductor_band_structure.py
+++ b/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__':
diff --git a/doc/source/tutorial/tutorial3.rst b/doc/source/tutorial/tutorial3.rst
index f5b603fa8ace912334efcc2ba4e7e5efcb057590..814ab761abb81f2aaf47913fc0df3205a64b46b6 100644
--- a/doc/source/tutorial/tutorial3.rst
+++ b/doc/source/tutorial/tutorial3.rst
@@ -31,11 +31,12 @@ 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 using `~kwant.physics.Bands`. For now we just plot the
+bandstructure:
.. literalinclude:: band_structure.py
:start-after: #HIDDEN_BEGIN_pejz
diff --git a/doc/source/whatsnew/0.3.rst b/doc/source/whatsnew/0.3.rst
index 577b705f86f4aed4211350352b2ea03bbda3f179..01823b4ea53b56153fb404b5153ea70b955b453e 100644
--- a/doc/source/whatsnew/0.3.rst
+++ b/doc/source/whatsnew/0.3.rst
@@ -9,6 +9,11 @@ Some renames
* ``MonatomicLattice`` has been renamed to `~kwant.lattice.Monatomic`,
* ``PolyatomicLattice`` has been renamed to `~kwant.lattice.Polyatomic`.
+Band structure plots
+--------------------
+A convenience function `~kwant.plotter.bands` for quick plotting of band
+structure was implemented.
+
Immutable site groups
---------------------
In order to make naming more consistent, `kwant.make_lattice` was renamed and
diff --git a/kwant/plotter.py b/kwant/plotter.py
index d1d276cb373bcab092b56f2f2b91c4e85bce90d4..07201851fcf19311c23c006feea6c52b8ae39f68 100644
--- a/kwant/plotter.py
+++ b/kwant/plotter.py
@@ -38,9 +38,9 @@ except ImportError:
"functions will work.", RuntimeWarning)
_mpl_enabled = False
-from . import system, builder
+from . import system, builder, physics
-__all__ = ['plot', 'map', 'sys_leads_sites', 'sys_leads_hoppings',
+__all__ = ['plot', 'map', 'bands', 'sys_leads_sites', 'sys_leads_hoppings',
'sys_leads_pos', 'sys_leads_hopping_pos', 'mask_interpolate']
@@ -849,6 +849,56 @@ def map(sys, value, colorbar=True, cmap=None,
fig.colorbar(image)
return output_fig(fig, file=file, show=show)
+
+def bands(sys, momenta=65, file=None, show=True, dpi=None, fig_size=None):
+ """Plot band structure of a translationally invariant 1D system.
+
+ Parameters
+ ----------
+ sys : kwant.system.InfiniteSystem
+ A system bands of which are to be plotted.
+ momenta : int or 1D array-like
+ Either a number of sampling points on the interval [-pi, pi], or an
+ array of points at which the band structure has to be evaluated.
+ file : string or file object or `None`
+ The output file. If `None`, output will be shown instead.
+ show : bool
+ Whether `matplotlib.pyplot.show()` is to be called, and the output is
+ to be shown immediately. Defaults to `True`.
+ dpi : float
+ Number of pixels per inch. If not set the `matplotlib` default is
+ used.
+ fig_size : tuple
+ Figure size `(width, height)` in inches. If not set, the default
+ `matplotlib` value is used.
+
+ Returns
+ -------
+ fig : matplotlib figure
+ A figure with the output.
+
+ Notes
+ -----
+ See `physics.Bands` for the calculation of dispersion without plotting.
+ """
+ momenta = np.array(momenta)
+ if momenta.ndim != 1:
+ momenta = np.linspace(-np.pi, np.pi, momenta)
+
+ bands = physics.Bands(sys)
+ energies = [bands(k) for k in momenta]
+
+ fig = Figure()
+ if dpi is not None:
+ fig.set_dpi(dpi)
+ if fig_size is not None:
+ fig.set_figwidth(fig_size[0])
+ fig.set_figheight(fig_size[1])
+ ax = fig.add_subplot(1, 1, 1)
+ ax.plot(momenta, energies)
+ return output_fig(fig, file=file, show=show)
+
+
# TODO (Anton): Fix plotting of parts of the system using color = np.nan.
# Not plotting sites currently works, not plotting hoppings does not.
# TODO (Anton): Allow a more flexible treatment of position than pos_transform