Blurb::Uses a file to import a user-specified MCMC proposal covariance.

Description::This keyword selection results in definition of the MCMC
proposal covariance from importing data a user-specified filename.
This import must be declared as either a full matrix or a matrix diagonal.

<b> Default Behavior </b>

This option is not the default, and generally implies special a priori
knowledge from the user.

<b> Usage Tips </b>

This option is not supported for the case of transformations to
standardized probability space.

Topics::

Examples::
\verbatim
method,									
        bayes_calibration queso
         samples = 1000 seed = 348
          dram
          proposal_covariance
            filename ... # See leaf nodes for required format option
\endverbatim

Theory::
Faq::
See_Also::
