[R] Odp: defining new variable

[Petr PIKAL]

Hi

r-help-bounces at r-project.org napsal dne 01.07.2011 14:32:31:

> B Marktplaats <gm.spam2011 at gmail.com> 
> Odeslal: r-help-bounces at r-project.org
> 
> 01.07.2011 14:32
> 
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> 
> r-help at r-project.org
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> [R] defining new variable
> 
> Hello,
> 
> I'm new to R and I'm trying to define new quite simple variable but I'm
> struggling with R syntax (when coming to dates) for a while and still
> getting <errors>  on it.
> 
> I would be very grateful if someone could help me with this, to be able 
to
> move on.
> 
> I have the following variables:
> 
>  - Transplant.date
>  - Faildate
>  - Death.date
> 
> The new variable Time should do the following thing:
> 
> Time <-
> 
>  If Not IsNull(<Faildate>) Then DaysBetween(<transplant date> 
,<Faildate>)
> Else If IsNull(<Faildate>) And Not IsNull(<Death date>) Then
> DaysBetween(<transplant date> ,<Death date>) Else If IsNull(<Faildate>) 
And
> IsNull(<Death date>) Then DaysBetween(<transplant date> ,CurrentDate())

I bet there is more elegant solution but

with such data frame you can

> df
          td         fd         dd
1 2011-06-11 2011-06-16       <NA>
2 2011-06-12       <NA> 2011-06-22
3 2011-06-13       <NA> 2011-06-23
4 2011-06-14       <NA> 2011-06-24
5 2011-06-15       <NA>       <NA>

df$days<-rowSums(sapply(df[,2:3], "-", df$td), na.rm=T)

Then you can check for NA values in fd and dd and change respective values 
by 

df$days[rowSums(is.na(df[,2:3]))==2] <- 
Sys.Date()-df$td[rowSums(is.na(df[,2:3]))==2]
df
          td         fd         dd days
1 2011-06-11 2011-06-16       <NA>    5
2 2011-06-12       <NA> 2011-06-22   10
3 2011-06-13       <NA> 2011-06-23   10
4 2011-06-14       <NA> 2011-06-24   10
5 2011-06-15       <NA>       <NA>   16
>

Regards
Petr


> 

> 
> 
> 
> Thank you very much!!
> 
> Laura
> 
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