# Setting parameter values:

Models, functions and probability distributions all take named
parameters in BAli-Phy. Parameters are in given square brackets:

   Model(parameter1=value,parameter2~distribution]

Values are given with `=`, and priors are given with `~`.
A value or prior for a parameter must be given, unless the
model or function has a default value specified.

For example, the Tamura-Nei (tn93) model has 3 parameters, `kappaPur`,
`kappaPyr`, and `pi` with default priors.  Focusing just on the first
parameter, the following are the same:

     tn93
     tn93(kappaPur~log_normal(log(2),0.5))

It is also possible to specify parameter values by position only:

     tn93(2,~log_normal(log(1),0.5))

The parameter names, order, type and default values for any function
can be found by giving that function name to the `help` command.
For example `bali-phy help tn93` gives information on the tn93 model.
