Summarises draws of a set of parameters by their mean vector and covariance
matrix. The result is a multivariate normal approximation to whatever the
draws describe, and it is the only route by which a covariance between
reported quantities reaches as_epidist_meta_model().
Details
The draws may be of any parameters. Posterior draws of a delay mean and
standard deviation, of a meanlog and sdlog, or of a shape and a
scale all give the same object. Nothing here checks that a parameter is
something a study could report, because that only matters when the object is
converted with as_epidist_estimates_data().
Draws may also cover a trajectory, with the parameters varying over an
index. The elements are then ordered index major and parameter minor, so a
mean and an sd over two index points give mean[1], sd[1], mean[2],
sd[2]. The order is fixed because the covariance is indexed by it.
There is no method for a vector of individual delays. Resampling delays manufactures a covariance the study never estimated, which is not what this represents.