Changeset 2260 for trunk/brian/library/random_processes.py

Timestamp:

11/29/10 13:04:18 (2 years ago)

Author:

crossant

Message:

added white_noise and colored_noise functions in brian.library.random_processes

Files:

• trunk/brian/library/random_processes.py (modified) (2 diffs)

trunk/brian/library/random_processes.py

@@ -4 +4 @@
 from brian.equations import Equations
 from brian.units import get_unit
+from scipy.signal import lfilter
+from numpy import exp, sqrt
+from numpy.random import randn
+from brian.stdunits import ms
+
+__all__ = ['OrnsteinUhlenbeck', 'white_noise', 'colored_noise']
 
 def OrnsteinUhlenbeck(x, mu, sigma, tau):
@@ -16 +22 @@
     return Equations('dx/dt=(mu-x)*invtau+sigma*((2.*invtau)**.5)*xi : unit', \
                      x=x, mu=mu, sigma=sigma, invtau=1. / tau, unit=get_unit(mu))
+
+
+def white_noise(dt, duration):
+    n = int(duration/dt)
+    noise = randn(n)
+    return noise
+
+def colored_noise(tau, dt, duration):
+    noise = white_noise(dt, duration)
+    a = [1., -exp(-dt/tau)]
+    b = [1.]
+    fnoise = sqrt(2*dt/tau)*lfilter(b, a, noise)
+    return fnoise
+
+if __name__ == '__main__':
+    tau = 10*ms
+    dt = .1*ms
+    duration = 1000*ms
+    noise = white_noise(dt, duration)
+    cnoise = colored_noise(tau, dt, duration)
+    from numpy import linspace
+    t = linspace(0*ms, duration, len(noise))
+    
+    from pylab import acorr, show, subplot, plot, ylabel, xlim
+    
+    subplot(221)
+    plot(t, noise)
+    ylabel('white noise')
+    
+    subplot(222)
+    acorr(noise, maxlags=200)
+    xlim(-200,200)
+    
+    subplot(223)
+    plot(t, cnoise)
+    ylabel('colored noise')
+    
+    subplot(224)
+    acorr(cnoise, maxlags=200)
+    xlim(-200,200)
+    
+    show()