par: a list of parameter values (ssw,ssv,pd,nyy,yr), where ssw is the standard deviation in the state equation, ssv is the standard deviation for the observation noise, pd is the probability to observe the true signal, nyy the dimension of the data, and yr is the range of the data.
xdim: the dimension of the state varible.
ydim: the dimension of the observation.
Returns
The function returns a list with the following components: - xx: the new sample.