Add some examples.

README.rst

@@ -61,6 +61,35 @@ few cases. For example, the simulator has a number of lattice fields that the
 live accelerator doesn't have; and the live machine has a few element fields
 that the simulator doesn't.
 
+Example
+^^^^^^^
+
+Note that you need an AT lattice that is compatible with Pytac. Some are provided
+in ``atip/rings/``, otherwise try running the Matlab function
+``atip/rings/create_lattice_matfile.m`` with an AT lattice loaded.
+
+.. code-block::
+
+    >>> import pytac
+    >>> import atip
+    >>> # Load the DIAD lattice from Pytac.
+    >>> lat = pytac.load_csv.load('DIAD')
+    >>> # Load the AT sim into the Pytac lattice.
+    >>> atip.load_sim.load_from_filepath(lat, 'atip/rings/diad.mat')
+    >>> # Use the sim by default.
+    >>> lat.set_default_data_source(pytac.SIM)
+    >>> # The initial beam position is zero.
+    >>> lat.get_value('x')
+    array([0., 0., 0., ..., 0., 0., 0.])
+    >>> # Get the first horizontal corrector magnet and set its current to 1A.
+    >>> hcor1 = lat.get_elements('HSTR')[0]
+    >>> hcor1.set_value('x_kick', 1, units=pytac.ENG)
+    >>> # Now the x beam position has changed.
+    >>> lat.get_value('x')
+    array([0.00240101, 0.00240101, 0.00239875, ..., 0.00240393, 0.00240327,
+           0.00240327])
+    >>>
+
 Virtual Accelerator:
 --------------------
 

docs/index.rst

@@ -35,6 +35,35 @@ This functionality is not documented here but an explanation of how it works
 and how to use it may be found in the ``.rst`` files inside ATIP's ``virtac``
 directory.
 
+Example
+-------
+
+Note that you need an AT lattice that is compatible with Pytac. Some are provided
+in ``atip/rings/``, otherwise try running the Matlab function
+``atip/rings/create_lattice_matfile.m`` with an AT lattice loaded.
+
+.. code-block::
+
+    >>> import pytac
+    >>> import atip
+    >>> # Load the DIAD lattice from Pytac.
+    >>> lat = pytac.load_csv.load('DIAD')
+    >>> # Load the AT sim into the Pytac lattice.
+    >>> atip.load_sim.load_from_filepath(lat, 'atip/rings/diad.mat')
+    >>> # Use the sim by default.
+    >>> lat.set_default_data_source(pytac.SIM)
+    >>> # The initial beam position is zero.
+    >>> lat.get_value('x')
+    array([0., 0., 0., ..., 0., 0., 0.])
+    >>> # Get the first horizontal corrector magnet and set its current to 1A.
+    >>> hcor1 = lat.get_elements('HSTR')[0]
+    >>> hcor1.set_value('x_kick', 1, units=pytac.ENG)
+    >>> # Now the x beam position has changed.
+    >>> lat.get_value('x')
+    array([0.00240101, 0.00240101, 0.00239875, ..., 0.00240393, 0.00240327,
+           0.00240327])
+    >>>
+
 Contents:
 =========