Allow non-integer incidence in projections

[sangeetabhatia03]

Would it be possible to allow non-integer incidence to be passed when using project? This is currently not possible as project accepts an incidence object, which can only take integer incidence.

This use-case has arisen because of a new feature in EpiEstim which allows estimating reproduction number from temporally aggregated incidence data. This works by first estimating a daily incidence time series from aggregated data. The reconstructed time series often contains non-integer incidence, which cannot be used to build an incidence object at the moment. Our current workaround is to force conversion into integer values but this is of course less than ideal, especially when incidence is low.

Since we often use incidence-EpiEstim-projections in tandem (as I am sure do other users of the recon ecosystem), it would be great if we can continue to use projections with the latest version of EpiEstim.

Proposed solution
Since building an incidence object from a linelist will necessarily lead to integer incidence, I think it would be difficult to incorporate this feature in its constructor. A potential solution could be edit the as.incidence method so that x doesn't have to contain integers. A flag check_int defaulting to TRUE would allow backward compatibility.