.. currentmodule:: brian

.. index::
   pair: example usage; run
   pair: example usage; PoissonGroup
   pair: example usage; spike_triggered_average
   pair: example usage; SpikeMonitor
   pair: example usage; exp

.. _example-misc_spike_triggered_average:

Example: spike_triggered_average (misc)
=======================================

Example of the use of the function spike_triggered_average. A white noise  is filtered
by a gaussian filter (low pass filter) which output is used to generate spikes (poission process)
Those spikes are used in conjunction with the input signal to retrieve the filter function.

::

    from brian import *
    from brian.hears import *
    from numpy.random import randn
    from numpy.linalg import norm
    from matplotlib import pyplot
    
    dt = 0.1*ms
    defaultclock.dt = dt
    stimulus_duration = 15000*ms
    stimulus = randn(int(stimulus_duration/     dt))
    
    #filter
    n=200
    filt = exp(-((linspace(0.5,n,n))-(n+5)/2)**2/(n/3));
    filt = filt/norm(filt)*1000;
    filtered_stimulus = convolve(stimulus,filt)
    
    
    neuron = PoissonGroup(1,lambda t:filtered_stimulus[int(t/dt)])
    
    spikes = SpikeMonitor(neuron)
    run(stimulus_duration,report='text')
    spikes = spikes[0] #resulting spikes
    
    max_interval = 20*ms #window duration of the spike triggered average
    onset = 10*ms
    sta,time_axis = spike_triggered_average(spikes,stimulus,max_interval,dt,onset=onset,display=True)
    
    
    figure()
    plot(time_axis,filt/max(filt))
    plot(time_axis,sta/max(sta))
    xlabel('time axis')
    ylabel('sta')
    legend(('real filter','estimated filter'))
    
    show()