想实现汇率的长记忆检验，步骤如下：

1.新建了一个data set，复制了汇率数据，名称为SDF1
2.套用讲义命令，得到以下：

tmp=acf(abs(SDF1),lag=200)
Warning messages:
  Data frames cannot be used in cts/its/rts, converting to matrix in: set.ts.class(x,
"rts", c(start = 1, deltat = 1, frequency = 1))
Problem in .Fortran("tsmiss8",: subroutine tsmiss8: Argument 1 has zero length
Use traceback() to see the call stack

求助，如何将data frames转为matrix呢？谢谢！