Next Generation Matrix Approach to Mask Effectiveness

The spreadsheet "masks" uses a simple next generation approach to explore the potential impact of mask use on COVID-19 R0 in communities.
Masks are effective in 2 ways: they prevent infection with COVID-19 in wearers; and prevent transmission by individuals with subclinical infection. The model permits assortative mixing (sheet = "Assortative"), based on the epsilon approach of Garnett and Anderson (https://academic.oup.com/jid/article/174/Supplement_2/S150/884972). The identity matrix in the extreme disassortative case is replaced by a matrix with zeroes in the diagonals.
The parameter "eta" defines assortativity in the assortative case (0 = random, 1 = extreme assortative), and disassortativity (0 = random, 1 = extreme disassortative) in the disassortative case.
For those unfamiliar with the next generation approach I have also included some classroom materials and a toy spreadsheet from the Dalla Lana School of Public Health, University of Toronto.