[amelia] How to format monthly dates for Time series analysis

Hi I am relatively new to R, and now trying Amelia for health indicator data I have a CSV file created from Excel with the following fields (columns): ID - autonumber identifier field Prov - name of the province (geographic area) for use as cross-section - this seems to work whether it is a string such as province acronym or whether coded to a number, although it doesn't work if I set the variable type to 'nominal' only if I leave it as 'no transformation' Month - this field is currently formatted as ISO dates, but this is being seen by Amelia (using AmeliaView) as a factor and is not working for doing time series with cross-section analysis eg of data 2006-12-01 2007-01-01 2007-02-01 2007-03-01 Value - the actual data values for the indicator as numbers - this is the field that has some missing data values that I want imputed. The only way I have been able to get this to work is to get Excel to convert the Month variable to a number - you then get data that looks like this 39052.00 39083.00 39114.00 39142.00 but I'm not sure if this is the correct way to do it and whether Amelia will understand the date/time significance. Otherwise how else must one format date variables so that they are correctly interpreted? Regards Candy -- Candy Day HealthLink, Health Systems Trust http://www.hst.org.za Mobile: 084 960 9014 Fax: 086 524 9563