不知道文档词条矩阵的结构里 i和j是什么意思，哪位大神给指点一下呗，万分感激。
> str(cmpDTM)
List of 6
$ i : int [1:613] 1 1 1 1 1 1 1 1 1 1 ...
$ j : int [1:613] 96 107 133 142 160 167 186 187 210 220 ...
$ v : num [1:613] 1 1 1 1 1 2 1 1 1 1 ...
$ nrow : int 30
$ ncol : int 529
$ dimnames:List of 2
..$ Docs : chr [1:30] "1" "2" "3" "4" ...
..$ Terms: chr [1:529] "abc" "aux" "bandgsm" "bbc" ...
- attr(*, "class")= chr [1:2] "DocumentTermMatrix" "simple_triplet_matrix"
- attr(*, "Weighting")= chr [1:2] "term frequency" "tf"
