How to extract two rows every three rows of the following matrix?
simple <- matrix(1:300,nrow=50,ncol=4)
CodePudding user response：
Another similar option
2 every 3
k=2
skp=3
unlist(sapply(seq(1,nrow(simple),k skp),function(x){x:(x k-1)},simplify=F))
[1] 1 2 6 7 11 12 16 17 21 22 26 27 31 32 36 37 41 42 46 47
7 every 3
k=7
skp=3
CodePudding user response：
Edit: generate a certain sequence
Generate the sequence you want to subset the rows like this:
rows <- sort(c(seq(1,nrow(simple), 5), seq(2,nrow(simple), 5)))
simple[rows,]
Output:
[,1] [,2] [,3] [,4]
[1,] 1 51 101 151
[2,] 2 52 102 152
[3,] 6 56 106 156
[4,] 7 57 107 157
[5,] 11 61 111 161
[6,] 12 62 112 162
[7,] 16 66 116 166
[8,] 17 67 117 167
[9,] 21 71 121 171
[10,] 22 72 122 172
[11,] 26 76 126 176
[12,] 27 77 127 177
[13,] 31 81 131 181
[14,] 32 82 132 182
[15,] 36 86 136 186
[16,] 37 87 137 187
[17,] 41 91 141 191
[18,] 42 92 142 192
[19,] 46 96 146 196
[20,] 47 97 147 197
Maybe you want this:
simple[seq_len(nrow(simple)) %% 3 != 0,]
Output:
[,1] [,2] [,3] [,4]
[1,] 1 51 101 151
[2,] 2 52 102 152
[3,] 4 54 104 154
[4,] 5 55 105 155
[5,] 7 57 107 157
[6,] 8 58 108 158
[7,] 10 60 110 160
[8,] 11 61 111 161
[9,] 13 63 113 163
[10,] 14 64 114 164
[11,] 16 66 116 166
[12,] 17 67 117 167
[13,] 19 69 119 169
[14,] 20 70 120 170
[15,] 22 72 122 172
[16,] 23 73 123 173
[17,] 25 75 125 175
[18,] 26 76 126 176
[19,] 28 78 128 178
[20,] 29 79 129 179
[21,] 31 81 131 181
[22,] 32 82 132 182
[23,] 34 84 134 184
[24,] 35 85 135 185
[25,] 37 87 137 187
[26,] 38 88 138 188
[27,] 40 90 140 190
[28,] 41 91 141 191
[29,] 43 93 143 193
[30,] 44 94 144 194
[31,] 46 96 146 196
[32,] 47 97 147 197
[33,] 49 99 149 199
[34,] 50 100 150 200