! 行列のインデックス要素の座標を返す


 > x = matrix(c(2,1,3,5,4,6,11,10,12,8,7,9),3,4)
 > x
     [,1] [,2] [,3] [,4]
 [1,]    2    5   11    8
 [2,]    1    4   10    7
 [3,]    3    6   12    9

 > x %>% arrayInd( c(3,4))
      [,1] [,2]
 [1,]    2    1
 [2,]    1    1
 [3,]    3    1
 [4,]    2    2
 [5,]    1    2
 [6,]    3    2
 [7,]    2    4
 [8,]    1    4
 [9,]    3    4
 [10,]    2    3
 [11,]    1    3
 [12,]    3    3