[R] can't read excel file with read.xls()

[array chip]

Hi, I encountered a problem of not being able to read in an excel spreadsheet using read.xls() in the xlsReadWrite package. can anyone help? Here is an example code


write.xls(matrix(1:9,nrow=3),"ttt.xls")
read.xls("ttt.xls")
Error in read.xls("ttt.xls") : 
  Unexpected error. Message: Can't find the file "ttt.xls"

The "ttt.xls" file was created in the current working folder successfully. 

Thanks

John