R and Excel

• Read xlsx file

  library(gdata)
  dat = read.xls('test.xlsx')
  

• Convert date

  ## So for recent dates from Windows Excel
  as.Date(35981, origin="1899-12-30") # 1998-07-05
  ## and Mac Excel
  as.Date(34519, origin="1904-01-01") # 1998-07-05
  
  # this works for me between Mac Excel and R
  weekdays(as.Date(41820, origin="1899-12-30"))
  

The above works for gdata 2.13.3, but not higher versions. For better solutions, read the following page about 'unambiguous date format:

http://stackoverflow.com/questions/14755425/what-are-the-standard-unambiguous-date-formats