R - 选择满足多个条件的矩阵行的最快方法

Question

这是对 returning the rows of a matrix that meet a condition 问题的扩展在 R. 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尽可能快地。这是我知道的方法:

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

显然应该有获取 final_out内容的方法在单行中，类似于: final_out <- which(mat$two == 7 && mat$three == 12)这比上面的两行代码更快更简洁。

返回此多条件矩阵查询的最快 R 代码是什么？

Answer 1

只需使用 [用逻辑比较子集...

#  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