PAM matrices

[enrico]

Hi,

I need to compute arbitrary time PAM matrices (where time is continuous 
and not discrete). I know that this is quite easy having the 
instantaneous rate matrix (i.e. P(i,j,t) = exp(Q*t)). Unfortunatly I 
wasn't able to find such rate matrix, is there someone who can help?

Thanks in advance.

Enrico Varriale