[R] "Missing value representation in Excel before extraction to R with RODBC"

[Fredrik Lundgren]

Dear list,

How should missing values be expressed in Excel before extraction to R 
via RODBC. I'm bewildered. Sometimes the representation with NA in Excel 
appears to work and shows up in R as <NA> but sometimes the use of NA in 
Excel changes the whole vector to NA's. Blank or nothing or NA as 
representation for missing values in Excel with dateformat gives NA's of 
the whole vector in R but with  general format in Excel gives blanks for 
missing values in R. How should I represent missing values in Excel?


Best wishes and thanks for any help
Fredrik Lundgren