[R] Calculating number of elapsed days from starting date

[Marcel Curlin]

Hi 
I have data for events in rows, with columns for person and date. Each
person may have more than one event;

tC <- textConnection("
Person	date
bob	1/1/00
bob	1/2/00
bob	1/3/00
dave	1/7/00
dave	1/8/00
dave	1/10/00
kevin	1/2/00
kevin	1/3/00
kevin	1/4/00
")
data <- read.table(header=TRUE, tC)
close.connection(tC)
rm(tC)

I would like to add a new column to my dataframe containing the calculated
number of elapsed days from the starting date for each person. So the new
dataframe would read

Person	date	Days
bob	1/1/00	0
bob	1/2/00	1
bob	1/3/00	2
dave	1/7/00	0
dave	1/8/00	1
dave	1/10/00	3
kevin	1/2/00	0
kevin	1/3/00	1
kevin	1/4/00	2

Not sure how to do this, tried looking through the forum but didn't find
anything that seemed to apply. Suggestions appreciated.




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