R中的稀疏事务

我正在处理POS数据，由于数据太大，我遇到了一个错误。我有835000行，我正试图进入一个事务表单，以使用arules包中的apriori算法

这就是我正在尝试的：

transactions = as(split(first2$Product_Desc,f=first2$Rtl_Id),"transactions")

它有以下错误：

Error: cannot allocate vector of size 45.7 Gb
In addition: Warning messages:
1: In unique(.Internal(unlist(lapply(x, levels), recursive, FALSE))) :
  Reached total allocation of 8103Mb: see help(memory.size)
2: In unique(.Internal(unlist(lapply(x, levels), recursive, FALSE))) :
  Reached total allocation of 8103Mb: see help(memory.size)
3: In unique(.Internal(unlist(lapply(x, levels), recursive, FALSE))) :
  Reached total allocation of 8103Mb: see help(memory.size)
4: In unique(.Internal(unlist(lapply(x, levels), recursive, FALSE))) :
  Reached total allocation of 8103Mb: see help(memory.size)

我怎样才能做到这一点