Fig. 4
From: Patterns of human social contact and mask wearing in high-risk groups in China
Contact matrices by age. Each cell of the matrix represents the mean number of contacts that an individual in a given age group has with other individuals, stratified by age group. The color intensity represents the number of individual contacts (A1–A5) or all contacts (B1–B5). To construct the matrix, we performed bootstrap sampling with replacement of survey participants weighted by the age distributions of the actual populations of Shanghai, Zhejiang, and Qinghai. Each cell of the matrix represents an average over 100 bootstrapped realizations