使用R创建稀疏矩阵

Question

I am trying to create a sparse matrix with my data containing userid, ISBN, and book rating. 

here is my data:

 User.ID       ISBN Book.Rating
 [1,]  276726  155061224           5
 [2,]  276727  446520802           0
 [3,]  276729  521795028           6
 [4,]  276733 2080674722           0
 [5,]  276736 3257224281           8
 [6,]  276737  600570967           6

Here is my code
 UIMatrix <- sparseMatrix(i = final.filtered["User.ID"],
                         j = final.filtered["ISBN"],
                          x = final.filtered["Book.Rating"])

    Error in sparseMatrix(i = final.filtered["User.ID"], j = final.filtered["ISBN"],  : 
      NA's in (i,j) are not allowed

我的数据中没有任何NA仍然会收到此错误。请告诉我如何解决此问题。我的稀疏矩阵包含userid作为行，ISBN作为列，Bookrating作为相应的值。