    MIX-GEN:  Generate hyperparameters randomly from the prior, or fix them.

    Mix-gen writes a series of independently-generated values for the
    hyperparameters of a mixture model to a log file.

    Usage:

        mix-gen log-file [ max-index ] [ "fix" [ SD-value ] ]

    Records of hyperparameters with indexes from zero up to the indicated
    index are generated (the default is max-index of zero).  If the log
    file already contains records with some of these indexes, only records
    with indexes greater than the last existing record are generated.

    If just max-index is specified, the hyperparameters are generated
    randomly from the prior, using the random number seed taken from the
    log file (eg, as specified by rand-seed).

    The "fix" option is useful for initializing iterative programs.  If it
    is given, the variable hyperparameters are not generated at random,
    but are instead set to fixed values.  The mean parameters will be
    fixed to zero.  The standard deviation hyperparameters will be fixed
    to the value given after "fix", or at the location parameter of their
    prior distribution, if no such value is specified.

    No data model is required to use mix-gen, but if a model is specified,
    the hyperparameters associated with it are generated as well.

    Note that mix-gen does not generate values for the parameters
    associated with particular mixture components.

                Copyright (c) 1995-2003 by Radford M. Neal