R-选择满足多个条件的矩阵行的最快方法 [英] R - fastest way to select the rows of a matrix that satisfy multiple conditions

问题描述

这是对返回R中满足条件的矩阵行.说我有矩阵:

       one two three four
 [1,]   1   6    11   16
 [2,]   2   7    12   17
 [3,]   3   8    11   18
 [4,]   4   9    11   19
 [5,]   5  10    15   20
 [6,]   1   6    15   20
 [7,]   5   7    12   20

我想返回所有行，其中matrix$two == 7和matrix$three == 12尽可能快.这是我知道的方法:

I want to return all rows, where matrix$two == 7 AND matrix$three == 12 as fast as possible. This is the way I know to do it:

 out <- mat[mat$two == 7,]
 final_out <- out[out$three == 12, ]

显然应该有一种方法可以单行获取final_out的内容，例如:final_out <- which(mat$two == 7 && mat$three == 12)，它比上面的两行代码更快，更简洁.

There should obviously be a method to get the contents of final_out in a one-liner, something like: final_out <- which(mat$two == 7 && mat$three == 12) that is faster and more succinct than the two line of codes above.

返回此多条件矩阵查询最快的R代码是什么?

What is the fastest R code to return this multiple condition matrix query?

推荐答案

只需在逻辑比较中使用[子设置...

Just use [ subsetting with logical comparison...

#  Reproducible data
set.seed(1)
m <- matrix( sample(12,28,repl=T) , 7 , 4 )
     [,1] [,2] [,3] [,4]
[1,]    4    8   10    3
[2,]    5    8    6    8
[3,]    7    1    9    2
[4,]   11    3   12    4
[5,]    3    3    5    5
[6,]   11    9   10    1
[7,]   12    5   12    5


#  Subset according to condition
m[ m[,2] == 3 & m[,3] == 12 , ]
[1] 11  3 12  4

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