The M matrix seems to be responsible The M matrix results in the most non-smooth sections of the things to which it is applied.  Seems to result from non-unity and non-smooth column normalization (note that M matrix is row normalized, but ideally is normalized in both dimensions, which is harder to enforce).  This in turn arises at least in part from leaky boundries -- probability density over the end of the boundary, and is thus worst near the matrix boundaries.  Computing on a larger grid than necessary and then displaying only inside of that might be a convenient way to avoid these problems.
The M matrix seems to be responsible
The M matrix results in the most non-smooth sections of the things to which it is applied.  Seems to result from non-unity and
non-smooth column normalization (note that M matrix is row normalized, but ideally is normalized in both dimensions, which
is harder to enforce).  This in turn arises at least in part from leaky boundries -- probability density over the end of the
boundary, and is thus worst near the matrix boundaries.  Computing on a larger grid than necessary and then displaying only inside
of that might be a convenient way to avoid these problems.

cboettig/multiple_uncertainty