Hello,
I gather variants of this question have been asked previously. I have
done some reading but only became more confused, as I suspect what I
am trying to do is more basic than other applications.
The following code readily calculates the difference in days between two dates:
newdays <- ISOdate(2005, 5,12) - ISOdate(2006, 12, 22)
However, I wanted to be able to deduct the dates in one variable from
the dates in another variable, resulting in a new variable - e.g the
difference in days between the two dates. Below is a sample of my
data. My questions:
1. I tried changing the data to dates via as.Date. Is this necessary
or do I need to alter the date format itself, e.g to 12/12/78 or some
other format?
2. I gather there are various packages as well as date formats.What
is the most straight forward approach to calculate the difference
between two dates, as below.
> dates <- read.csv("c:\\dates.csv",header=T)
> dates
v1 v2
1 12/12/1978 12/12/2005
2 23/01/1965 23/09/2001
3 24/12/2004 16/03/2007
4 3/03/2003 4/04/2004
5 8/11/2006 1/05/2007
> class(dates$v1)
[1] "factor"
> class(dates$v2)
[1] "factor"
> dates <- read.csv("c:\\dates.csv",header=T,
as.Date(as.character(dates) "%d/%m/%Y"))
Error: syntax error, unexpected STR_CONST, expecting ',' in "dates <-
read.csv("c:\\dates.csv",header=T, as.Date(as.character(dates) "%d/%m/%Y""
>
Any assistance is much appreciated,
Bob
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