This function generatea a time series of one dimension
Brownian motion, adapted from
http://cos.name/wp-content/uploads/2008/12/stochastic-differential-equation-with-r.pdf
.
Usage
bm(x0 = 0, t0 = 0, t = 1, n = 100)
Arguments
x0
the start value, with the default value 0
t0
the start time point, with the default value 0
t
the end time point, with the default value 1
n
the number of points between t0 and t that will
be generated, with the default value 100