=================
Injecting current
=================

.. testsetup::

   from pyNN.mock import *
   setup()
   population = Population(30, IF_cond_exp())

Current waveforms are represented in PyNN by :class:`CurrentSource` classes.
There are four built-in source types, and it is straightforward to
implement your own.

There are two ways to inject a current waveform into the cells of a
:class:`Population`, :class:`PopulationView` or :class:`Assembly`: either the
:meth:`inject_into()` method of the :class:`CurrentSource` or the
:meth:`inject()` method of the :class:`Population`, :class:`Assembly`, etc.

.. doctest::

    >>> pulse = DCSource(amplitude=0.5, start=20.0, stop=80.0)
    >>> pulse.inject_into(population[3:7])

.. .. plot:: pyplots/dc_source.py

.. image:: images/dc_source.png


.. doctest::

    >>> sine = ACSource(start=50.0, stop=450.0, amplitude=1.0, offset=1.0,
    ...                 frequency=10.0, phase=180.0)
    >>> population.inject(sine)

.. .. plot:: pyplots/ac_source.py

.. image:: images/ac_source.png


.. doctest::

    >>> steps = StepCurrentSource(times=[50.0, 110.0, 150.0, 210.0],
    ...                           amplitudes=[0.4, 0.6, -0.2, 0.2])
    >>> steps.inject_into(population[(6,11,27)])

.. .. plot:: pyplots/step_source.py

.. image:: images/step_source.png


.. doctest::

    >>> noise = NoisyCurrentSource(mean=1.5, stdev=1.0, start=50.0, stop=450.0, dt=1.0)
    >>> population.inject(noise)

.. .. plot:: pyplots/noise_source.py

.. image:: images/noise_source.png


For a full description of all the built-in current source classes, see the
:doc:`API reference <reference/electrodes>`.

.. todo:: write "implementing-your-own-current-source" (e.g., implement "chirp")