R help - Mar 2008 - build.mim() from the minet package

Hi,

I am trying to contstruct a mutual informtation matrix using the 
function build.mim() from the minet package:

 > build.mim(myData, estimator="empirical")

and I have two questions.

1.) The estimator "empirical" computes the entropy of the empirical 
probability distribution. This probably means it is using this 
definition of the entropy: H = sum_x sum_y p(x,y)* log( p(x,y)/ 
(p(x)*p(x)) ). Is this correct?
2.) Which is basis is used for the log?


Thanks a lot for your in advance.

Bettina Keller