[R] Odp: Getting the month out of my date as a number not characters

[Petr PIKAL]

Hi

Tim Chatterton <tim.chatterton at uwe.ac.uk> napsal dne 02.07.2009 13:19:46:

>  > Actually it is a character and you  need to convert it to numbers by 
as.numeric
> 
> This is the bit I have problems with - I can easily get it out as 
characters 
> but I cannot work out how to use as.numeric (and had actually given up 
as it 
> seemed to only want to work on numeric fields not character fields).
> 
> Any idea how I do the character to numeric conversion?
> Thanks,
> Tim.

What is the problem with

> format(strptime("20/2/06 11:16:16.683", "%d/%m/%y %H:%M:%OS"), "%m")
[1] "02"
> as.numeric(format(strptime("20/2/06 11:16:16.683", "%d/%m/%y 
%H:%M:%OS"), "%m"))
[1] 2

Regards
Petr


> 
> 
> Petr PIKAL wrote: 
> Hi
> 
> r-help-bounces at r-project.org napsal dne 02.07.2009 12:40:05:
> 
> 
> I have a data frame (hf) that is all set up and the dates are working 
> fine - however I need to extract the months and hours (2 separate 
> columns) as numbers - however they are coming out as characters.
> 
> I have tried both the following:
> 
> hf50$hour=  hf50$date
> hf50$hour=format(hf50["hour"],"%H")
> 
> and
> 
> hf$month <- as.POSIXct(strptime(hf$date, format = "%m"))
> 
> 
> If hf$date is in POSIX format then
> 
> format(hf$date,"%m")
> 
> shall give you month as a number 01-12. Actually it is a character and 
you 
> need to convert it to numbers by as.numeric.
> 
> If it is in different format then depending on how it is actually 
> formatted you can use strptime to transform it to POSIX class and then 
to 
> use format to extract only days or months from it.
> 
> Regards
> Petr
> 
> 
> 
> 
> but they are still coming out as characters.
> 
> Any ideas please?
> Thanks,
> Tim.
> 
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> __________________________________________
> 
> Dr Tim Chatterton
> Senior Research Fellow
> Air Quality Management Resource Centre
> Faculty of Environment and Technology
> University of the West of England
> Frenchay Campus
> Bristol
> BS16 1QY
> 
> Tel: 0117 328 2929
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> Email: Tim.Chatterton at uwe.ac.uk