I have already derived vertex connections of the graph. It is a matrix with 3 columns. Column 1 contains vertex i, column 2 contains all its adjacent vertexes, column 3 contains the edge weight, so the data are already processed into something like {{1,1,0.8} {1, 3, 0.4}, {2, 3, 0.5} ...}
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Yet I do not know how to incorporate this into igraph in R. Seems to me all presented igraph work are initiated from matrix containing original raw data.