Hello Petia,
I am not quite sure if I understand your problem. The voltmeter records time, sender and voltage for each data point. In the following example, it records the voltage of two neurons. Then
voltmeter.get('events')
returns
{'senders': array([1, 2, 1, ..., 2, 1, 2]), 'times': array([ 1., 1., 2., ..., 998., 999., 999.]), 'V_m': array([-68.56875477, -70. , -67.27371053, ..., -69.89028023, -57.39686729, -69.90055242])}
Entries in the senders, times and V_m arrays correspond to each other, so you can group data by sender.
Also when recording to file, sender information is recorded:
# NEST version: 3.5 # RecordingBackendASCII version: 2 sender time_ms V_m 1 1.000 -68.569 2 1.000 -70.000 1 2.000 -67.274 2 2.000 -70.000
Best, Hans Ekkehard