Hi Lara, You want to subset out 20% of the columns from a matrix, at random. Try:
combinations <- combn(20,3) ## makes the 'all combinations' matrix sample <- combinations[,sample(1:ncol(combinations), floor(ncol(combinations)*0.2))] ## subsets out 20% of the columns from that object. ## Note that sample() samples without replacement, by default. sample Hope that helps! Shane On Tue, 26 Feb 2019 at 12:38, Lara Silva <lara.sfp.si...@gmail.com> wrote: > Hello, > > I want to select sets of combinations, but I do not want use all 1140 > > combn (20,3) > > choose (20,3) - total of 1140. > > [,1091] [,1092] [,1093] [,1094] [,1095] [,1096] [,1097] [,1098] [,1099] > [,1100] > [1,] 13 13 13 13 13 13 13 13 > 13 13 > [2,] 15 15 15 15 15 16 16 16 > 16 17 > [3,] 16 17 18 19 20 17 18 19 > 20 18 > [,1101] [,1102] [,1103] [,1104] [,1105] [,1106] [,1107] [,1108] > [,1109] [,1110] > [1,] 13 13 13 13 13 14 14 14 > 14 14 > [2,] 17 17 18 18 19 15 15 15 > 15 15 > [3,] 19 20 19 20 20 16 17 18 > 19 20 > [,1111] [,1112] [,1113] [,1114] [,1115] [,1116] [,1117] [,1118] > [,1119] [,1120] > [1,] 14 14 14 14 14 14 14 14 > 14 14 > [2,] 16 16 16 16 17 17 17 18 > 18 19 > [3,] 17 18 19 20 18 19 20 19 > 20 20 > [,1121] [,1122] [,1123] [,1124] [,1125] [,1126] [,1127] [,1128] > [,1129] [,1130] > [1,] 15 15 15 15 15 15 15 15 > 15 15 > [2,] 16 16 16 16 17 17 17 18 > 18 19 > [3,] 17 18 19 20 18 19 20 19 > 20 20 > [,1131] [,1132] [,1133] [,1134] [,1135] [,1136] [,1137] [,1138] > [,1139] [,1140] > [1,] 16 16 16 16 16 16 17 17 > 17 18 > [2,] 17 17 17 18 18 19 18 18 > 19 19 > [3,] 18 19 20 19 20 20 19 20 > 20 20 > > > If it possible to select 20% of this combinations (sets)? > It is important to generate a random sample ... > > Example > > 15 1 8 ... > 16 7 20.... > 17 20 13... > > Any advice? > > Thanks, > > Lara > > [[alternative HTML version deleted]] > > _______________________________________________ > R-sig-ecology mailing list > R-sig-ecology@r-project.org > https://stat.ethz.ch/mailman/listinfo/r-sig-ecology > [[alternative HTML version deleted]] _______________________________________________ R-sig-ecology mailing list R-sig-ecology@r-project.org https://stat.ethz.ch/mailman/listinfo/r-sig-ecology
