比较两个矩阵之间的行 [英] Comparing rows between two matrices

问题描述

是否存在一种快速的方法来查找矩阵B中存在矩阵A的哪些行? 例如

Is there a fast way of finding which rows in matrix A are present in matrix B? e.g.

m1 = matrix(c(1:6), ncol=2, byrow = T); m2 = matrix(c(1:4), ncol=2, byrow=T);

结果将是1、2.

矩阵的行数不相同(列数相同)，它们有些大-行数从10 ^ 6-10 ^ 7.

The matrices do not have the same number of rows (number of columns is the same), and they are somewhat big - from 10^6 - 10^7 number of rows.

我目前所知道的最快的方法是:

The fastest way of doing it, that I know of for now, is:

duplicated(rbind(m1, m2))

Tnx！

推荐答案

该尺寸的快速方法应该是:

A fast way for that size should be :

require(data.table)
M1 = setkey(data.table(m1))
M2 = setkey(data.table(m2))
na.omit(
    M2[M1,which=TRUE]
)
[1] 1 2

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