On 26-03-2012, at 21:57, Sam Steingold wrote: > when subsetting a matrix results in a single row, it is converted to a > vector, not a matrix. > how do I avoid this? > > 1. __GOOD__ > >> edges <- get.edges(g,E(g)) >> edges > [,1] [,2] > [1,] 0 2 > [2,] 0 3 > [3,] 0 4 > [4,] 0 5 > [5,] 1 1 > [6,] 0 4 > [7,] 0 6 > [8,] 0 7 > [9,] 0 8 > [10,] 0 9 > [11,] 0 5 > [12,] 0 10 > [13,] 0 11 > [14,] 0 12 > [15,] 0 11 > [16,] 0 13 > [17,] 0 14 > [18,] 0 15 > [19,] 0 16 > [20,] 1 17 > [21,] 1 11 > [22,] 0 11 >> loops <- edges[,1] == edges[,2] >> loopless <- edges[!loops,] >> loopless > loopless > [,1] [,2] > [1,] 0 2 > [2,] 0 3 > [3,] 0 4 > [4,] 0 5 > [5,] 0 4 > [6,] 0 6 > [7,] 0 7 > [8,] 0 8 > [9,] 0 9 > [10,] 0 5 > [11,] 0 10 > [12,] 0 11 > [13,] 0 12 > [14,] 0 11 > [15,] 0 13 > [16,] 0 14 > [17,] 0 15 > [18,] 0 16 > [19,] 1 17 > [20,] 1 11 > [21,] 0 11 >> unique(loopless[,1]) > [1] 0 1 > > 2. __BAD__ >> edges > [,1] [,2] > [1,] 0 1 > [2,] 0 0 > Browse[1]> edges[!loops,] > [1] 0 1
?`[` Use drop=FALSE Berend ______________________________________________ [email protected] mailing list https://stat.ethz.ch/mailman/listinfo/r-help PLEASE do read the posting guide http://www.R-project.org/posting-guide.html and provide commented, minimal, self-contained, reproducible code.
