[英]extract sparse rows from sparse matrix in r
I have a large sparse matrix to analyze in R. For instance: 我有一个大的稀疏矩阵在R中进行分析。例如:
i <- c(1,3:8); j <- c(2,9,6:10); x <- 7 * (1:7)
(A <- sparseMatrix(i, j, x = x))
[1,] . 7 . . . . . . . .
[2,] . . . . . . . . . .
[3,] . . . . . . . . 14 .
[4,] . . . . . 21 . . . .
[5,] . . . . . . 28 . . .
[6,] . . . . . . . 35 . .
[7,] . . . . . . . . 42 .
[8,] . . . . . . . . . 49
I want to extract the i -th row from this matrix, as a sparse vector. 我想从这个矩阵中提取第i行,作为稀疏向量。 If I write
如果我写
(x=A[1,])
I obtain 我知道了
[1] 0 7 0 0 0 0 0 0 0 0
but what I would like is 但我想要的是
[1] . 7 . . . . . . . .
What I expect is that the new vector does not materialize the zeros. 我期望的是新的向量不会实现零。 How can I do this?
我怎样才能做到这一点?
Thanks 谢谢
You can use drop = FALSE
: 你可以使用
drop = FALSE
:
A[1, , drop = FALSE]
# 1 x 10 sparse Matrix of class "dgCMatrix"
#
# [1,] . 7 . . . . . . . .
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