Pgbrown geometric brownian motion pattern

superclass: Pbrown

Pgbrown(lo, hi, step, length)

Returns a stream that behaves like a geometric brownian motion. 

lo, hi - lower and upper boundary of values  (default: 0.0 and 1.0)

step - maximum multiplication factor per step (omega) - the distribution is xrand2.  (default: 0.125)

length - number of values produced (default: inf)

See also: BrownNoise, Pbrown

// example

(

var a, b;

a = Pgbrown(0.0, 1.0, 0.2, inf);

b = a.asStream;

7.do({ b.next.postln; });

)

// sound example

(

SynthDef(\help_sinegrain, 

{ arg out=0, freq=440, sustain=0.05;

var env;

env = EnvGen.kr(Env.perc(0.01, sustain, 0.2), doneAction:2);

Out.ar(out, SinOsc.ar(freq, 0, env))

}).add;

)

(

var a;

a = Pgbrown(1.0, 2.0, 0.1, inf).asStream;

Routine({

loop({

Synth(\help_sinegrain, [\freq, a.next * 600 + 300]);

0.02.wait;

})

}).play;

)

// compare with normal brownian motion:

(

var a;

a = Pbrown(1.0, 2.0, 0.1, inf).asStream;

Routine({

loop({

Synth(\help_sinegrain, [\freq, a.next * 600 + 300]);

0.02.wait;

})

}).play;

)