Question

我如何抽取<代码>m>哪里<代码>a哪怕? 例如,

m = matrix(1:24, 6)
a = c(3, 4, 1, 1, 2, 5)

Answer 1

你的问题不明确,但我认为我知道你的含义。您的数据:

m = matrix(1:24, 6)
a = c(3, 4, 1, 1, 2, 5)

您可以表示,你希望选择<代码>m的所有行文,哪怕是<代码>a。因此,在这种情况下,你希望second <>/em>和fifthrows of m,因为只有a的第二和第五部分。在此情况下,这项工作将:



 m[a %% 2 ==0,]

不过,我认为,你指的是希望找到<代码>a中哪怕是(此处为2和4)的数字,然后选择<代码>m。在这种情况下,你将使用:

m[a[a %% 2 ==0],]

So that would select first the fourth, and then the second row of m. Remember, however, that if you have any even number in there twice, it will select the row twice.

If you wanted to select the rows in order (row 2 and then row 4) you would do:

m[sort(a[a %% 2 ==0]),]

Answer 2

引言

m[which(a %% 2 != 0), ]

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