[英]How do I get the intersect of two matrices?
# These are the two matrices that I would like to subset based on identical
# entries within entire rows.
mata <- matrix(c("A", "B", "C", "F", "D", "E", "F", "G"),
nrow = 4, ncol = 2,
dimnames = list(c(), c("A", "B")))
mata
## A B
## [1,] "A" "D"
## [2,] "B" "E"
## [3,] "C" "F"
## [4,] "F" "G"
matb <- matrix(c("B", "A", "C", "F", "M", "D", "D", "H", "G", "X"),
nrow = 5, ncol = 2,
dimnames = list(c(), c("A", "B")))
matb
## A B
## [1,] "B" "D"
## [2,] "A" "D"
## [3,] "C" "H"
## [4,] "F" "G"
## [5,] "M" "X"
If the two matrices were not unordered and of the same length, the following code should work and would be efficient. 如果两个矩阵没有无序且长度相同,则以下代码应该起作用并且效率很高。
mata[rowMeans(mata == matb) == 1, ]
A hackish solution of mine would be the concatenation of the individual columns of each matrix that I want to use for the matching. 我的一个hackish解决方案是我想要用于匹配的每个矩阵的各列的串联。 In this example I will use all columns. 在这个例子中,我将使用所有列。
mata <- cbind(mata, C = paste0(mata[, "A"], "_", mata[, "B"]))
matb <- cbind(matb, C = paste0(matb[, "A"], "_", matb[, "B"]))
mata[mata[, "C"] %in% matb[, "C"], colnames(mata) != "C"]
## A B
## [1,] "A" "D"
## [2,] "F" "G"
This is the result that I am looking for, but I am wondering whether there is something more elegant such as the %in%
function for vectors. 这是我正在寻找的结果,但我想知道是否有一些更优雅的东西,例如矢量的%in%
函数。
The solution should apply to general cases where the matrices are not necessarily of equal length. 该解决方案应适用于矩阵长度不一定相等的一般情况。
You could use the function merge()
for this: 你可以使用函数merge()
:
> merge(mata,matb)
A B
1 A D
2 F G
If you load dplyr, intersect.data.frame
is added: 如果加载dplyr,则添加intersect.data.frame
:
library(dplyr)
options(stringsAsFactors=FALSE)
dfa <- as.data.frame(mata)
dfb <- as.data.frame(matb)
intersect(dfa,dfb)
# A B
# 1 A D
# 2 F G
Similarly, union
, setequal
(testing set equality) and setdiff
(set minus) are available. 类似地, union
, setequal
(测试集相等)和setdiff
(set minus)可用。
Aside. 在旁边。 Each row of a data.frame corresponds to an observation, so it makes sense to talk about intersecting two sets of observations (two data.frames). data.frame的每一行对应一个观察,因此讨论交叉的两组观察(两个data.frames)是有意义的。 For matrices, however, it really does not make sense. 然而,对于矩阵来说,它确实没有意义。 That's why hacks like the OP's solution and @RHertel's (which coerces to data.frame behind the scenes) are needed for this operation if you want to continue using matrices. 这就是为什么如果你想继续使用矩阵,这个操作需要像OP的解决方案和@ RHertel(它强制在幕后的data.frame)这样的黑客攻击。
声明:本站的技术帖子网页,遵循CC BY-SA 4.0协议,如果您需要转载,请注明本站网址或者原文地址。任何问题请咨询:yoyou2525@163.com.