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Stefano Sofia

2016-Apr-11 07:22 UTC

[R] Query about use of format in strptime

Dear R-list users,
I need to use strptime because I have to deal with date with hours and minutes.
I read the manual for strptime and I also looked at many examples, but when I
try to apply it to my code, I always encounter some problems.
I try to change the default format, with no success. Why? How can I change the
format?

1.
init_day <- as.factor("2015-02-24-00-30")
strptime(init_day, format="%Y-%m-%d-%H-%M")
[1] "2015-02-24 00:30:00"
It works, but why also seconds are shown if in format seconds are not specified?

2.
init_day <- as.factor("2015-02-24-0-00")
strptime(init_day, format="%Y-%m-%d-%H-%M")
[1] "2015-02-24"
Again, the specified format is not applied. Why?

Thank you for your attention and your help
Stefano


________________________________

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Jim Lemon

2016-Apr-11 07:47 UTC

head link

[R] Query about use of format in strptime

Hi Stefano,
As the help page says:

"The default for the format methods is "%Y-%m-%d %H:%M:%S" if any
element has a time component which is not midnight, and "%Y-%m-%d"
otherwise. This is because when the result is printed, it uses the
default format. If you want a specified output representation:

format(strptime(init_day, format="%Y-%m-%d-%H-%M"),"%Y-%M-%d
%H:%M")
[1] "2015-30-24 00:30"

For the "midnight" case:

format(strptime(init_day, format="%Y-%m-%d-%H-%M"),"%Y-%m-%d
%H:%M")
[1] "2015-02-24 00:00"

Jim


On Mon, Apr 11, 2016 at 5:22 PM, Stefano Sofia
<stefano.sofia at regione.marche.it> wrote:> Dear R-list users,
> I need to use strptime because I have to deal with date with hours and
minutes.
> I read the manual for strptime and I also looked at many examples, but when
I try to apply it to my code, I always encounter some problems.
> I try to change the default format, with no success. Why? How can I change
the format?
>
> 1.
> init_day <- as.factor("2015-02-24-00-30")
> strptime(init_day, format="%Y-%m-%d-%H-%M")
> [1] "2015-02-24 00:30:00"
> It works, but why also seconds are shown if in format seconds are not
specified?
>
> 2.
> init_day <- as.factor("2015-02-24-0-00")
> strptime(init_day, format="%Y-%m-%d-%H-%M")
> [1] "2015-02-24"
> Again, the specified format is not applied. Why?
>
> Thank you for your attention and your help
> Stefano
>
>
> ________________________________
>
> AVVISO IMPORTANTE: Questo messaggio di posta elettronica pu? contenere
informazioni confidenziali, pertanto ? destinato solo a persone autorizzate alla
ricezione. I messaggi di posta elettronica per i client di Regione Marche
possono contenere informazioni confidenziali e con privilegi legali. Se non si ?
il destinatario specificato, non leggere, copiare, inoltrare o archiviare questo
messaggio. Se si ? ricevuto questo messaggio per errore, inoltrarlo al mittente
ed eliminarlo completamente dal sistema del proprio computer. Ai sensi dell?art.
6 della DGR n. 1394/2008 si segnala che, in caso di necessit? ed urgenza, la
risposta al presente messaggio di posta elettronica pu? essere visionata da
persone estranee al destinatario.
> IMPORTANT NOTICE: This e-mail message is intended to be received only by
persons entitled to receive the confidential information it may contain. E-mail
messages to clients of Regione Marche may contain information that is
confidential and legally privileged. Please do not read, copy, forward, or store
this message unless you are an intended recipient of it. If you have received
this message in error, please forward it to the sender and delete it completely
from your computer system.
>
>         [[alternative HTML version deleted]]
>
> ______________________________________________
> R-help at r-project.org mailing list -- To UNSUBSCRIBE and more, see
> 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.

Enrico Schumann

2016-Apr-11 07:55 UTC

head link

[R] Query about use of format in strptime

On Mon, 11 Apr 2016, Stefano Sofia <stefano.sofia at regione.marche.it>
writes:
> Dear R-list users,
> I need to use strptime because I have to deal with date with hours and
minutes.
> I read the manual for strptime and I also looked at many examples, but when
I try to apply it to my code, I always encounter some problems.
> I try to change the default format, with no success. Why? How can I change
the format?
>
> 1.
> init_day <- as.factor("2015-02-24-00-30")
> strptime(init_day, format="%Y-%m-%d-%H-%M")
> [1] "2015-02-24 00:30:00"
> It works, but why also seconds are shown if in format seconds are not
specified?
>
> 2.
> init_day <- as.factor("2015-02-24-0-00")
> strptime(init_day, format="%Y-%m-%d-%H-%M")
> [1] "2015-02-24"
> Again, the specified format is not applied. Why?
>
> Thank you for your attention and your help
> Stefano

strptime creates a POSIXlt object, and the specified format
tells it how to interpret the string you pass in. (Your
factor is converted to character by strptime.)

If you want to have the POSIXlt object printed in a
particular way, use ?strftime or ?format.

  > format(strptime(init_day, format="%Y-%m-%d-%H-%M"),
"%Y-%m-%d-%H-%M")
  ## [1] "2015-02-24-00-00"


-- 
Enrico Schumann
Lucerne, Switzerland
http://enricoschumann.net

Stefano Sofia

2016-Apr-11 08:48 UTC

head link

[R] Query about use of format in strptime

Dear Jim and dear Enrico,
thank you for your replies.
Unfortunately your hints didn't solve my problem, and I am getting mad.
Can I show you my whole process? I will be as quick as possible.
I start from a data frame called Snow of the form

year month day hh mm hs
2007 11 19 0 0 0.00
2007 11 19 0 30 0.00
2007 11 19 1 0 0.00
2007 11 19 1 30 0.00
2007 11 19 2 0 0.00
2007 11 19 2 30 0.00
2007 11 19 3 0 0.00
2007 11 19 3 30 0.00
2007 11 19 4 0 0.00
2007 11 19 4 30 0.00
...

whth semi-hourly data.
I need to deal with date so I used strptime:

Snow$data_factor <- as.factor(paste(Snow$year, Snow$month, Snow$day, Snow$hh,
Snow$mm, sep="-"))
Snow$data_strptime <- strptime(Snow$data_factor, format =
"%Y-%m-%d-%H-%M")

It gives me

year month day hh mm hs  data_factor  data_strptime
1     2007    11  19  0  0  0  2007-11-19-0-0 2007-11-19 00:00:00
2     2007    11  19  0 30  0  2007-11-19-0-30  2007-11-19 00:30:00
3     2007    11  19  1  0  0  2007-11-19-1-0  2007-11-19 01:00:00
4     2007    11  19  1 30  0  2007-11-19-1-30  2007-11-19 01:30:00
5     2007    11  19  2  0  0  2007-11-19-2-0  2007-11-19 02:00:00
6     2007    11  19  2 30  0  2007-11-19-2-30  2007-11-19 02:30:00
7     2007    11  19  3  0  0  2007-11-19-3-0  2007-11-19 03:00:00
8     2007    11  19  3 30  0  2007-11-19-3-30  2007-11-19 03:30:00
9     2007    11  19  4  0  0  2007-11-19-4-0  2007-11-19 04:00:00
10   2007    11  19  4 30  0  2007-11-19-4-30  2007-11-19 04:30:00
...

The type of the column data_strptime is
$data_strptime
[1] "POSIXlt" "POSIXt"

Because of some days (or part of them) might be missing, given a time interval I
want to create a new data frame with all time-steps and then merge the new data
frame with the old one.
In order to create a new data frame with all time-steps, I thought to use

df_new <- data.frame(data_strptime=seq(init_day, fin_day, by="30
mins"))

and then

Snow_all <- merge(df_new, Snow, by=("data_strptime"), all.x=TRUE)

My problem is in dealing with init_day and fin_day, respectively for example
"200711190000" and "200711210000".
I am not able to create a sequence of class "POSIXlt"
"POSIXt", in order to merge the two data frames.

Could you please help me in this?
Thank you again for your attention
Stefano

________________________________________
Da: Jim Lemon [drjimlemon at gmail.com]
Inviato: luned? 11 aprile 2016 9.47
A: Stefano Sofia
Cc: r-help at r-project.org
Oggetto: Re: [R] Query about use of format in strptime

Hi Stefano,
As the help page says:

"The default for the format methods is "%Y-%m-%d %H:%M:%S" if any
element has a time component which is not midnight, and "%Y-%m-%d"
otherwise. This is because when the result is printed, it uses the
default format. If you want a specified output representation:

format(strptime(init_day, format="%Y-%m-%d-%H-%M"),"%Y-%M-%d
%H:%M")
[1] "2015-30-24 00:30"

For the "midnight" case:

format(strptime(init_day, format="%Y-%m-%d-%H-%M"),"%Y-%m-%d
%H:%M")
[1] "2015-02-24 00:00"

Jim

On Mon, Apr 11, 2016 at 5:22 PM, Stefano Sofia
<stefano.sofia at regione.marche.it> wrote:> Dear R-list users,
> I need to use strptime because I have to deal with date with hours and
minutes.
> I read the manual for strptime and I also looked at many examples, but when
I try to apply it to my code, I always encounter some problems.
> I try to change the default format, with no success. Why? How can I change
the format?
>
> 1.
> init_day <- as.factor("2015-02-24-00-30")
> strptime(init_day, format="%Y-%m-%d-%H-%M")
> [1] "2015-02-24 00:30:00"
> It works, but why also seconds are shown if in format seconds are not
specified?
>
> 2.
> init_day <- as.factor("2015-02-24-0-00")
> strptime(init_day, format="%Y-%m-%d-%H-%M")
> [1] "2015-02-24"
> Again, the specified format is not applied. Why?
>
> Thank you for your attention and your help
> Stefano
>
>
> ________________________________
>
> AVVISO IMPORTANTE: Questo messaggio di posta elettronica pu? contenere
informazioni confidenziali, pertanto ? destinato solo a persone autorizzate alla
ricezione. I messaggi di posta elettronica per i client di Regione Marche
possono contenere informazioni confidenziali e con privilegi legali. Se non si ?
il destinatario specificato, non leggere, copiare, inoltrare o archiviare questo
messaggio. Se si ? ricevuto questo messaggio per errore, inoltrarlo al mittente
ed eliminarlo completamente dal sistema del proprio computer. Ai sensi dell?art.
6 della DGR n. 1394/2008 si segnala che, in caso di necessit? ed urgenza, la
risposta al presente messaggio di posta elettronica pu? essere visionata da
persone estranee al destinatario.
> IMPORTANT NOTICE: This e-mail message is intended to be received only by
persons entitled to receive the confidential information it may contain. E-mail
messages to clients of Regione Marche may contain information that is
confidential and legally privileged. Please do not read, copy, forward, or store
this message unless you are an intended recipient of it. If you have received
this message in error, please forward it to the sender and delete it completely
from your computer system.
>
>         [[alternative HTML version deleted]]
>
> ______________________________________________
> R-help at r-project.org mailing list -- To UNSUBSCRIBE and more, see
> 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.
________________________________

AVVISO IMPORTANTE: Questo messaggio di posta elettronica pu? contenere
informazioni confidenziali, pertanto ? destinato solo a persone autorizzate alla
ricezione. I messaggi di posta elettronica per i client di Regione Marche
possono contenere informazioni confidenziali e con privilegi legali. Se non si ?
il destinatario specificato, non leggere, copiare, inoltrare o archiviare questo
messaggio. Se si ? ricevuto questo messaggio per errore, inoltrarlo al mittente
ed eliminarlo completamente dal sistema del proprio computer. Ai sensi dell?art.
6 della DGR n. 1394/2008 si segnala che, in caso di necessit? ed urgenza, la
risposta al presente messaggio di posta elettronica pu? essere visionata da
persone estranee al destinatario.
IMPORTANT NOTICE: This e-mail message is intended to be received only by persons
entitled to receive the confidential information it may contain. E-mail messages
to clients of Regione Marche may contain information that is confidential and
legally privileged. Please do not read, copy, forward, or store this message
unless you are an intended recipient of it. If you have received this message in
error, please forward it to the sender and delete it completely from your
computer system.

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