将行追加到dataframe—因子问题。

I have a large dataframe (14552 rows by 15 columns) containing billing data from 2001 to 2007. I have used sqlFetch to get 2008 data. In order to append the 2008 data to the data of the preceding 7 years one would do as followsI have a large dataframe (14552 rows by 15 colu