Question

我有一个矩阵，看起来像这样

myMatrix <- matrix(data = TRUE, nrow = 3, ncol = 3)
myMatrix[as.matrix(expand.grid(1:2, 1:2))] <- FALSE

myMatrix

      [,1]  [,2] [,3]
[1,] FALSE FALSE TRUE
[2,] FALSE FALSE TRUE
[3,]  TRUE  TRUE TRUE

我想得到一个列出所有行和列索引的数据框或矩阵，其中myMatrix是TRUE：

  column row
1      3   1
2      3   2
3      1   3
4      2   3
5      3   3

我该怎么做？

Answer 1

我们可以使用select p.billing_cycle_in_months, avg(t.days) from ( select *, datediff(day,transaction_settled_at, transaction_refunded_at) as days, dense_rank() over (partition by signup_id order by transaction_settled_at asc) as rank from transactions ) t join signups s on s.signup_id = t.signup_id join plans p on p.id = s.plan_id where datediff(year,s.started_at, current_date) > 1 and t.rank = 1 group by p.billing_cycle_in_months

which

或使用which(myMatrix, arr.ind = TRUE)并指定arrayInd

Answer 2

我们可以使用row和col来获取矩阵中每个元素的行索引和列索引，并使用TRUE的逻辑值对myMatrix值进行子集化。

data.frame(column = col(myMatrix)[myMatrix], row = row(myMatrix)[myMatrix])

满足条件的矩阵索引

2 个答案: