R help - Jun 2010 - difference in dates

Dear R People:

I have a data frame with the two following date columns:

> a.df[1:10,c(1,6)]
           DATE      DEATH
1207 2009-04-16 2009-05-06
1514 2009-04-16 2009-05-06
2548 2009-04-16 2009-05-08
3430 2009-04-16 2009-05-09
3851 2009-04-16 2009-05-09
3945 2009-04-16 2009-05-09
7274 2009-04-16 2009-05-12
7532 2009-04-16 2009-05-12
7651 2009-04-16 2009-05-12
8495 2009-04-16 2009-05-13
>
I would like to generate a 3rd column which is the difference in days
between the two dates.

I tried

a.df$DEATH - a.df$DATE

but I obtain all NA.

Any help would be much appreciated.

Thanks,
Erin



-- 
Erin Hodgess
Associate Professor
Department of Computer and Mathematical Sciences
University of Houston - Downtown
mailto: erinm.hodgess at gmail.com

Are you sure your data was the Date class?
> x <- read.table('clipboard', header=TRUE)
> x
           DATE      DEATH
1207 2009-04-16 2009-05-06
1514 2009-04-16 2009-05-06
2548 2009-04-16 2009-05-08
3430 2009-04-16 2009-05-09
3851 2009-04-16 2009-05-09
3945 2009-04-16 2009-05-09
7274 2009-04-16 2009-05-12
7532 2009-04-16 2009-05-12
7651 2009-04-16 2009-05-12
8495 2009-04-16 2009-05-13
> ?as.Date
> x$DATE <- as.Date(x$DATE)
> x$DEATH <- as.Date(x$DEATH)
> x$length <- x$DEATH - x$DATE
> x
           DATE      DEATH  length
1207 2009-04-16 2009-05-06 20 days
1514 2009-04-16 2009-05-06 20 days
2548 2009-04-16 2009-05-08 22 days
3430 2009-04-16 2009-05-09 23 days
3851 2009-04-16 2009-05-09 23 days
3945 2009-04-16 2009-05-09 23 days
7274 2009-04-16 2009-05-12 26 days
7532 2009-04-16 2009-05-12 26 days
7651 2009-04-16 2009-05-12 26 days
8495 2009-04-16 2009-05-13 27 days


On Sun, Jun 20, 2010 at 8:13 PM, Erin Hodgess <erinm.hodgess at gmail.com>
wrote:
> Dear R People:
>
> I have a data frame with the two following date columns:
>
>
>> a.df[1:10,c(1,6)]
> ? ? ? ? ? DATE ? ? ?DEATH
> 1207 2009-04-16 2009-05-06
> 1514 2009-04-16 2009-05-06
> 2548 2009-04-16 2009-05-08
> 3430 2009-04-16 2009-05-09
> 3851 2009-04-16 2009-05-09
> 3945 2009-04-16 2009-05-09
> 7274 2009-04-16 2009-05-12
> 7532 2009-04-16 2009-05-12
> 7651 2009-04-16 2009-05-12
> 8495 2009-04-16 2009-05-13
>>
>
> I would like to generate a 3rd column which is the difference in days
> between the two dates.
>
> I tried
>
> a.df$DEATH - a.df$DATE
>
> but I obtain all NA.
>
> Any help would be much appreciated.
>
> Thanks,
> Erin
>
>
>
> --
> Erin Hodgess
> Associate Professor
> Department of Computer and Mathematical Sciences
> University of Houston - Downtown
> mailto: erinm.hodgess at gmail.com
>
> ______________________________________________
> R-help at r-project.org mailing list
> https://stat.ethz.ch/mailman/listinfo/r-help
> PLEASE do read the posting guide
http://www.R-project.org/posting-guide.html
> and provide commented, minimal, self-contained, reproducible code.
>


-- 
Jim Holtman
Cincinnati, OH
+1 513 646 9390

What is the problem that you are trying to solve?

Hi, 
Are you sure these are date objects and not strings? For example
> d1<-runif(10,0,100)
> d2<-runif(10,0,200)
>
df<-data.frame(d1=d1+as.Date("2010-6-20")+d1,d2=as.Date("2009-6-20")+d2)
> df
           d1         d2
1  2010-09-23 2009-06-30
2  2010-06-25 2009-08-21
3  2010-10-10 2009-08-04
4  2010-07-06 2009-07-30
5  2010-07-05 2009-10-19
6  2010-07-07 2009-08-01
7  2010-11-09 2009-09-25
8  2010-07-19 2009-12-03
9  2010-12-24 2009-07-19
10 2010-09-25 2009-06-27
> df$DD<-df$d1-df$d2
> df
           d1         d2            DD
1  2010-09-23 2009-06-30 449.7866 days
2  2010-06-25 2009-08-21 307.0807 days
3  2010-10-10 2009-08-04 431.7428 days
4  2010-07-06 2009-07-30 341.2171 days
5  2010-07-05 2009-10-19 259.0490 days
6  2010-07-07 2009-08-01 339.7433 days
7  2010-11-09 2009-09-25 410.1609 days
8  2010-07-19 2009-12-03 227.1901 days
9  2010-12-24 2009-07-19 523.5030 days
10 2010-09-25 2009-06-27 454.6529 days

generates differences between the 2 columns without NAs. 
What's the output you get when you call str on your data frame?

Christos 

> Date: Sun, 20 Jun 2010 19:13:24 -0500
> From: erinm.hodgess@gmail.com
> To: r-help@stat.math.ethz.ch
> Subject: [R]  difference in dates
> 
> Dear R People:
> 
> I have a data frame with the two following date columns:
> 
> 
> > a.df[1:10,c(1,6)]
>            DATE      DEATH
> 1207 2009-04-16 2009-05-06
> 1514 2009-04-16 2009-05-06
> 2548 2009-04-16 2009-05-08
> 3430 2009-04-16 2009-05-09
> 3851 2009-04-16 2009-05-09
> 3945 2009-04-16 2009-05-09
> 7274 2009-04-16 2009-05-12
> 7532 2009-04-16 2009-05-12
> 7651 2009-04-16 2009-05-12
> 8495 2009-04-16 2009-05-13
> >
> 
> I would like to generate a 3rd column which is the difference in days
> between the two dates.
> 
> I tried
> 
> a.df$DEATH - a.df$DATE
> 
> but I obtain all NA.
> 
> Any help would be much appreciated.
> 
> Thanks,
> Erin
> 
> 
> 
> -- 
> Erin Hodgess
> Associate Professor
> Department of Computer and Mathematical Sciences
> University of Houston - Downtown
> mailto: erinm.hodgess@gmail.com
> 
> ______________________________________________
> R-help@r-project.org mailing list
> https://stat.ethz.ch/mailman/listinfo/r-help
> PLEASE do read the posting guide
http://www.R-project.org/posting-guide.html
> and provide commented, minimal, self-contained, reproducible code.
 		 	   		  
_________________________________________________________________
Hotmail: Powerful Free email with security by Microsoft.

	[[alternative HTML version deleted]]