Extend fitting functions to simultaneously fit to multiple datasets + add other datasets for contact surveys (like polymod)

[njtierney]

e.g., fit the model to data from Melbourne and polymod simultaneously.

[goldingn]

Rolls et al: https://bmcinfectdis.biomedcentral.com/articles/10.1186/s12879-015-1237-9

[njtierney]

@goldingn , just wanted to confirm that this is about having other datasets to have inside the {conmat} package?

[goldingn]

I think the priority is extending the fitting functions so they can simultaneously fit to multiple datasets (polymod plus something smaller). Including other datasets in the package would be nice but is less important, since people will probably have their own that they can't necessarily share

[njtierney]

Yup, makes sense.

[njtierney]

Not sure how to implement the simultaneous fitting to multiple datasets off the top of my head, though!