[R] add only the 1st of May with POSIXct

[Stefano Sofia]

Sorry for the delay of my answer.

Enrico and Rui, thank you for your help.

Both solutions worked well, in particular Enrico's hint is very easy to implement.


Thank you

Stefano


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Stefano Sofia PhD
Civil Protection - Marche Region - Italy
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________________________________
Da: Enrico Schumann <es using enricoschumann.net>
Inviato: mercoled� 29 maggio 2024 08:15
A: Stefano Sofia
Cc: r-help using R-project.org
Oggetto: Re: [R] add only the 1st of May with POSIXct

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On Tue, 28 May 2024, Stefano Sofia writes:

> Dear R-list users,
>
> From an initial and a final date I create a sequence of days using POSIXct.
>
> If this interval covers all or only in part the months from May to October, I need to get rid of the days from the 2nd of May to the 31st of October:
>
>
> a <- as.POSIXct("2002-11-01", format = "%Y-%m-%d", tz="Etc/GMT-1")
>
> b <- as.POSIXct("2004-06-01", format = "%Y-%m-%d", tz="Etc/GMT-1")
>
> mydf <- data.frame(data_POSIX=seq(as.POSIXct(paste(format(a, "%Y-%m-%d"), "09:00:00", sep=""), format="%Y-%m-%d %H:%M:%S", tz="Etc/GMT-1"), as.POSIXct(paste(format(b, "%Y-%m-%d"), "09:00:00", sep=""), format="%Y-%m-%d %H:%M:%S", tz="Etc/GMT-1"), by="1 day"))
>
>
> If I execute
>
> as.data.frame(mydf[format(mydf$data_POSIX,"%m") %in% c("11", "12", "01", "02", "03", "04"), ])
>
> the interval will be
>
> from 2002-11-01 09:00:00 to 2003-04-30 09:00:00
>
> and from 2003-11-01 09:00:00 to 2004-04-30 09:00:00
>
>
> but I need also 2003-05-01 09:00:00 and 2004-05-01 09:00:00
>
>
> How can I solve this problem?
>
>
> Thank you for your attention and your help
>
> Stefano
>

I think this could be simplified a bit:

    a <- as.POSIXct("2002-11-01 09", format = "%Y-%m-%d %H", tz="Etc/GMT-1")
    b <- as.POSIXct("2004-06-01 09", format = "%Y-%m-%d %H", tz="Etc/GMT-1")

Create your sequence:

    S <- seq(a, b , by = "1 day")
    month.day <- format(S, "%m-%d")

Now subset S for those days that you want:

    S[month.day <= "05-01" | month.day > "10-31"]


--
Enrico Schumann
Lucerne, Switzerland
https://eur02.safelinks.protection.outlook.com/?url=http%3A%2F%2Fenricoschumann.net%2F&data=05%7C02%7Cstefano.sofia%40regione.marche.it%7Cfb03eb5bf2e24b4b76b408dc7fa6b98e%7C295eaa1431a14b09bfe65a338b679f60%7C0%7C0%7C638525601265102204%7CUnknown%7CTWFpbGZsb3d8eyJWIjoiMC4wLjAwMDAiLCJQIjoiV2luMzIiLCJBTiI6Ik1haWwiLCJXVCI6Mn0%3D%7C0%7C%7C%7C&sdata=46TUwFWwpLcdtZGARpDkhnuHhgZ546khJI%2FONPeYXe4%3D&reserved=0

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