multimeter – Sampling continuous quantities from neurons ======================================================== Description +++++++++++ Most sampling use cases are covered by the ``multimeter``, which allows to record analog values from neurons. Models which have such values expose a ``recordables`` property that lists all recordable quantities. This property can be inspected using ``GetDefaults`` on the model class or ``GetStatus`` on a model instance. It cannot be changed by the user. :: >>> nest.GetDefaults('iaf_cond_alpha')['recordables'] ['g_ex', 'g_in', 't_ref_remaining', 'V_m'] The ``record_from`` property of a ``multimeter`` (a list, empty by default) can be set to contain the name(s) of one or more of these recordables to have them sampled during simulation. :: mm = nest.Create('multimeter', 1, {'record_from': ['V_m', 'g_ex']}) The sampling interval for recordings (given in ms) can be controlled using the ``multimeter`` parameter ``interval``. The default value of 1.0 ms can be changed by supplying a new value either in the call to ``Create`` or by using ``SetStatus`` on the model instance. :: nest.SetStatus(mm, 'interval': 0.1}) The recording interval must be greater than or equal to the :ref:`simulation resolution `, which defaults to 0.1 ms. .. warning:: The set of variables to record from and the recording interval must be set **before** the ``multimeter`` is connected to any neuron. These properties cannot be changed afterwards. After configuration, a ``multimeter`` can be connected to the neurons it should record from by using the standard ``Connect`` routine. :: neurons = nest.Create('iaf_psc_alpha', 100) nest.Connect(mm, neurons) To learn more about possible connection patterns and additional options when using ``Connect``, see the guide on :ref:`connection management `. The above call to ``Connect`` would fail if the neurons would not support the sampling of the values ``V_m`` and ``g_ex``. It would also fail if carried out in the wrong direction, that is , trying to connect the neurons to `mm`. .. note:: A pre-configured ``multimeter`` is available under the name ``voltmeter``. Its ``record_from`` property is already set to record the variable ``V_m`` from the neurons it is connected to. .. include:: ../models/recording_device.rst record_from A list (default: `[]`) of parameters and state variables to sample from the nodes, the multimeter is connected to. Potential recordables are given in the corresponding model documentation. interval A float (default: 1.0) specifying the interval in ms, at which data is collected from the nodes, the multimeter is connected to. See also ++++++++ :doc:`Device `, :doc:`Recorder `