deviance: Deviance
In annecori/mRIIDSprocessData: Epidemiological forcasting using real-time data

Deviance at a given set of parameters. Deviance is a measure of the model discrepancy and is defined as -2 times the log likelihood.

1	deviance(I0, pij, R, si, x)

`I0`	T X N matrix of incidence
`pij`	N X N. Element i, j is the probability of moving from i to j.
`R`	either 1 X N matrix of reproduction numbers in each location at t or T X N matrix of reproduction numbers in each location at each time step from 1 to t.
`si`	A vector drawn from serial interval distribution. If the length of the vector is less than T, it is padded with 0s.
`x`	N X 1 vector of observed incidence at step t.