[R] chron is.weekend() function

[David James]

Hi Paul,

This is clearly a bug -- the argument needs to be coerced 
to a "dates" class argument, since the underlying algorithm relies 
on integer arithmetic (date+time objects are represented as
floating point numbers).

Thus you can use is.weekend(dates(mb.df$dtg)) as a workaround.  

(I'll send you a fix later on).

Paul Hewson wrote:
> Hello,
> 
> I have a dataset which has fields giving both calendar date and weekday.   I
> know better functions are now available, but I am still using chron because
> of the is.holiday() function and a homemade (even Heath Robinson would be
> ashamed) is.daylight() function. 
> 
> As a check for typos in the data input, I checked that the dates matched the
> weekdays.   I'm getting some confusing results from the is.weekend function
> in chron.   For example (in US format: mm/dd/yy):
> 
> > mb.df$dtg[is.weekend(mb.df$dtg) == FALSE & mb.df$Weekday == "Sun"]
>   [1] (09/24/00 11:52:00) (07/30/00 13:30:00) (04/30/00 15:30:00)
>   [4] (04/30/00 16:28:00) (06/04/00 17:35:00) (09/03/00 14:45:00)
>   [7] (05/07/00 16:42:00) (12/17/00 11:55:00) (08/20/00 10:20:00)
>  [10] (01/07/01 20:32:00) (06/18/00 15:45:00) (09/24/00 11:16:00)
>  [13] (09/10/00 20:35:00) (03/18/00 17:50:00) (09/03/00 09:20:00)
>  [16] (06/18/00 14:37:00) (09/24/00 15:47:00) (09/03/00 20:38:00)
> 
> I have checked most of these dates on my calendar and it agrees with the
> original dataset that they are in fact Sundays.   Also, I note that
> is.weekend() seems to think that Fridays from 2000 onwards are weekends.
> 
> The dataset contains data from 1996 until early 2001 and chron's
> is.weekend() resolved dates correctly prior to 2000.   From the command line
> however more recent dates are also resolved correctly.   For example I
> tried:
> 
> > is.weekend("09/02/01")
>  [1] TRUE
> 
> and
> 
> > is.weekend("09/03/01")
>  [1] FALSE
> 
> which is correct and therefore gives me some worries about my data, but I
> would really appreciate any ideas as to where I should start looking.
> 
> Thanks
> 
> Paul
> 
> This was run on R 1.3.0 on Mandrake 7.1 with chron 2.2-17   
> 
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> Data Analyst and Research Officer
> 
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-- 
David A. James
Statistics Research, Room 2C-253            Phone:  (908) 582-3082       
Bell Labs, Lucent Technologies              Fax:    (908) 582-3340
Murray Hill, NJ 09794-0636
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