R help - Mar 2007 - No years() function?

Hi,

I'm trying to aggregate date values using the aggregate function. For
example:

aggregate(data,by=list(weekdays(LM),months(LM)),FUN=length)

I would also like to aggregate by year but there seems to be no
years() function.
Should there be one? Is there any alternative choice?

Also, a hours() function would be great. Any tip on this?

Thanks in advance!
S?rgio Nunes

S?rgio Nunes <snunes <at> gmail.com> writes:
> 
> Hi,
> 
> I'm trying to aggregate date values using the aggregate function. For
example:
> 
> aggregate(data,by=list(weekdays(LM),months(LM)),FUN=length)
> 
> I would also like to aggregate by year but there seems to be no
> years() function.
> Should there be one? Is there any alternative choice?
> 
> Also, a hours() function would be great. Any tip on this?
> 
> Thanks in advance!
> S?rgio Nunes
> 
  Well, working by analogy with the existing
functions, this might work (not messing with
setting up an S3 default though):
> apropos("weekdays")
[1] "weekdays"        "weekdays.Date"  
"weekdays.POSIXt"
> weekdays.Date
function (x, abbreviate = FALSE)
format(x, ifelse(abbreviate, "%a", "%A"))
<environment: namespace:base>


d1 = Sys.time()

years <- function(x,abbreviate=FALSE) {
  as.numeric(format(x, ifelse(abbreviate, "%y", "%Y")))
}

hours <- function(x) {
   as.numeric(format(x,"%H"))
}

years(d1); hours(d1)

>From the help of weekdays:
"Note:

     Other components such as the day of the month or the year are very
     easy to compute: just use 'as.POSIXlt' and extract the relevant
     component."

Yet another option:

help(package="chron")

JR

El mi?, 07-03-2007 a las 15:35 +0000, S?rgio Nunes
escribi?:
> Hi,
> 
> I'm trying to aggregate date values using the aggregate function. For
example:
> 
> aggregate(data,by=list(weekdays(LM),months(LM)),FUN=length)
> 
> I would also like to aggregate by year but there seems to be no
> years() function.
> Should there be one? Is there any alternative choice?
> 
> Also, a hours() function would be great. Any tip on this?
> 
> Thanks in advance!
> S?rgio Nunes
> 
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-- 
Dipl.-Biol. JR Ferrer Paris
~~~~~~~~~~~~~~~~~~~~~~~~~~~
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