[Dart-help] xrate sqrt

[argriffi <arg...@nc...>]

Hi,

I would like to use XRate to estimate a reversible model with a 
constraint similar to the RIND constraint.  The RIND constraint is 
R_{ij} \propto pi_j, and I would like to estimate a codon model with a 
constraint that R_{ij} \propto sqrt(pi_aa_j / pi_aa_i).  The XRate model 
specification language doesn't seem to allow square roots.  Is this an 
extension that I could add, or would it be fundamentally incompatible 
with what XRate is doing?

Alex