Dear R-list users,
this question will seem silly to most of you, but I really got mad trying to
find a solution with no success, and therefore I decided to write here.
Suppose I create the following data frame:
mydf <- data.frame(date = c("2007-11-19 00:00:00.000",
"2007-11-19 06:00:00.000", "2007-11-19 12:00:00.000",
"2007-11-19 18:00:00.000", "2007-11-20 00:00:00.000"), value
= rep(10, 5))
mydf$data_POSIX <- as.POSIXct(mydf$date, format = "%Y-%m-%d
%H:%M:%S", tz="Etc/GMT-1")
max(mydf$data_POSIX)
gives, obviously,
[1] "2007-11-20 +01"
Now if I export this data frame in a txt file
write.table(mydf, file="mydf.txt", sep = ",",
dec=".", row.names=FALSE, col.names = TRUE, quote=FALSE)
the file is stored like
date,value,data_POSIX
2007-11-19 00:00:00.000,10,2007-11-19
2007-11-19 06:00:00.000,10,2007-11-19 06:00:00
2007-11-19 12:00:00.000,10,2007-11-19 12:00:00
2007-11-19 18:00:00.000,10,2007-11-19 18:00:00
2007-11-20 00:00:00.000,10,2007-11-20
Hours, minutes and seconds at 00 are not shown anymore.
When I read back this file into R:
mydf2 <- read.table(file="mydf.txt", header = TRUE,
sep=",", dec = ".")
mydf2$data_POSIX <- as.POSIXct(mydf2$data_POSIX, format = "%Y-%m-%d
%H:%M:%S", tz="Etc/GMT-1")
I get
date value data_POSIX
1 2007-11-19 00:00:00.000 10 <NA>
2 2007-11-19 06:00:00.000 10 2007-11-19 06:00:00
3 2007-11-19 12:00:00.000 10 2007-11-19 12:00:00
4 2007-11-19 18:00:00.000 10 2007-11-19 18:00:00
5 2007-11-20 00:00:00.000 10 <NA>
and
max(mydf2$data_POSIX)
does not work anymore.
Where is my mistake? Is there a solution?
Thank you for your attention and your help
Stefano
(oo)
--oOO--( )--OOo--------------------------------------
Stefano Sofia MSc, PhD
Civil Protection Department - Marche Region - Italy
Meteo Section
Snow Section
Via Colle Ameno 5
60126 Torrette di Ancona, Ancona (AN)
Uff: +39 071 806 7743
E-mail: stefano.sofia at regione.marche.it
---Oo---------oO----------------------------------------
________________________________
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R does this for convenience when printing values. But it's not always convenient when writing to a file. Instead, you could use strftime to convert to your desired character format before writing: mydf$data_POSIX <- strftime(mydf$data_POSIX, "%Y-%m-%d %H:%M:%OS3") you can optionally change the 3 to a number between 0 and 6. If you choose 0, it's easier to just use %S instead. On Fri, Nov 14, 2025, 12:30 Stefano Sofia via R-help <r-help at r-project.org> wrote:> Dear R-list users, > > this question will seem silly to most of you, but I really got mad trying > to find a solution with no success, and therefore I decided to write here. > > > Suppose I create the following data frame: > > > mydf <- data.frame(date = c("2007-11-19 00:00:00.000", "2007-11-19 > 06:00:00.000", "2007-11-19 12:00:00.000", "2007-11-19 18:00:00.000", > "2007-11-20 00:00:00.000"), value = rep(10, 5)) > > mydf$data_POSIX <- as.POSIXct(mydf$date, format = "%Y-%m-%d %H:%M:%S", > tz="Etc/GMT-1") > > max(mydf$data_POSIX) > > > gives, obviously, > > > [1] "2007-11-20 +01" > > > Now if I export this data frame in a txt file > > > write.table(mydf, file="mydf.txt", sep = ",", dec=".", row.names=FALSE, > col.names = TRUE, quote=FALSE) > > > the file is stored like > > > date,value,data_POSIX > 2007-11-19 00:00:00.000,10,2007-11-19 > 2007-11-19 06:00:00.000,10,2007-11-19 06:00:00 > 2007-11-19 12:00:00.000,10,2007-11-19 12:00:00 > 2007-11-19 18:00:00.000,10,2007-11-19 18:00:00 > 2007-11-20 00:00:00.000,10,2007-11-20 > > Hours, minutes and seconds at 00 are not shown anymore. > When I read back this file into R: > > mydf2 <- read.table(file="mydf.txt", header = TRUE, sep=",", dec = ".") > > mydf2$data_POSIX <- as.POSIXct(mydf2$data_POSIX, format = "%Y-%m-%d > %H:%M:%S", tz="Etc/GMT-1") > > I get > date value data_POSIX > 1 2007-11-19 00:00:00.000 10 <NA> > 2 2007-11-19 06:00:00.000 10 2007-11-19 06:00:00 > 3 2007-11-19 12:00:00.000 10 2007-11-19 12:00:00 > 4 2007-11-19 18:00:00.000 10 2007-11-19 18:00:00 > 5 2007-11-20 00:00:00.000 10 <NA> > > and > > max(mydf2$data_POSIX) > > > does not work anymore. > > Where is my mistake? Is there a solution? > > Thank you for your attention and your help > > Stefano > > > > > > (oo) > --oOO--( )--OOo-------------------------------------- > Stefano Sofia MSc, PhD > Civil Protection Department - Marche Region - Italy > Meteo Section > Snow Section > Via Colle Ameno 5 > 60126 Torrette di Ancona, Ancona (AN) > Uff: +39 071 806 7743 > E-mail: stefano.sofia at regione.marche.it > ---Oo---------oO---------------------------------------- > > ________________________________ > > 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. Ai sensi dell'art. 2.4 dell'allegato 1 alla > DGR n. 74/2021, 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 > https://www.R-project.org/posting-guide.html > and provide commented, minimal, self-contained, reproducible code. >[[alternative HTML version deleted]]
?s 17:30 de 14/11/2025, Stefano Sofia via R-help escreveu:> Dear R-list users, > > this question will seem silly to most of you, but I really got mad trying to find a solution with no success, and therefore I decided to write here. > > > Suppose I create the following data frame: > > > mydf <- data.frame(date = c("2007-11-19 00:00:00.000", "2007-11-19 06:00:00.000", "2007-11-19 12:00:00.000", "2007-11-19 18:00:00.000", "2007-11-20 00:00:00.000"), value = rep(10, 5)) > > mydf$data_POSIX <- as.POSIXct(mydf$date, format = "%Y-%m-%d %H:%M:%S", tz="Etc/GMT-1") > > max(mydf$data_POSIX) > > > gives, obviously, > > > [1] "2007-11-20 +01" > > > Now if I export this data frame in a txt file > > > write.table(mydf, file="mydf.txt", sep = ",", dec=".", row.names=FALSE, col.names = TRUE, quote=FALSE) > > > the file is stored like > > > date,value,data_POSIX > 2007-11-19 00:00:00.000,10,2007-11-19 > 2007-11-19 06:00:00.000,10,2007-11-19 06:00:00 > 2007-11-19 12:00:00.000,10,2007-11-19 12:00:00 > 2007-11-19 18:00:00.000,10,2007-11-19 18:00:00 > 2007-11-20 00:00:00.000,10,2007-11-20 > > Hours, minutes and seconds at 00 are not shown anymore. > When I read back this file into R: > > mydf2 <- read.table(file="mydf.txt", header = TRUE, sep=",", dec = ".") > > mydf2$data_POSIX <- as.POSIXct(mydf2$data_POSIX, format = "%Y-%m-%d %H:%M:%S", tz="Etc/GMT-1") > > I get > date value data_POSIX > 1 2007-11-19 00:00:00.000 10 <NA> > 2 2007-11-19 06:00:00.000 10 2007-11-19 06:00:00 > 3 2007-11-19 12:00:00.000 10 2007-11-19 12:00:00 > 4 2007-11-19 18:00:00.000 10 2007-11-19 18:00:00 > 5 2007-11-20 00:00:00.000 10 <NA> > > and > > max(mydf2$data_POSIX) > > > does not work anymore. > > Where is my mistake? Is there a solution? > > Thank you for your attention and your help > > Stefano > > > > > > (oo) > --oOO--( )--OOo-------------------------------------- > Stefano Sofia MSc, PhD > Civil Protection Department - Marche Region - Italy > Meteo Section > Snow Section > Via Colle Ameno 5 > 60126 Torrette di Ancona, Ancona (AN) > Uff: +39 071 806 7743 > E-mail: stefano.sofia at regione.marche.it > ---Oo---------oO---------------------------------------- > > ________________________________ > > 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. Ai sensi dell'art. 2.4 dell'allegato 1 alla DGR n. 74/2021, 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 https://www.R-project.org/posting-guide.html > and provide commented, minimal, self-contained, reproducible code.Hello, Instead of as.POSIXct use strftime. In the second code line below. mydf <- data.frame(date = c("2007-11-19 00:00:00.000", "2007-11-19 06:00:00.000", "2007-11-19 12:00:00.000", "2007-11-19 18:00:00.000", "2007-11-20 00:00:00.000"), value = rep(10, 5)) mydf$data_POSIX <- strftime(mydf$date, format = "%Y-%m-%d %H:%M:%S", tz="Etc/GMT-1") max(mydf$data_POSIX) #> [1] "2007-11-20 00:00:00" write.table(mydf, file="mydf.txt", sep = ",", dec=".", row.names=FALSE, col.names = TRUE, quote=FALSE) mydf2 <- read.table(file="mydf.txt", header = TRUE, sep=",", dec = ".") mydf2 #> date value data_POSIX #> 1 2007-11-19 00:00:00.000 10 2007-11-19 00:00:00 #> 2 2007-11-19 06:00:00.000 10 2007-11-19 06:00:00 #> 3 2007-11-19 12:00:00.000 10 2007-11-19 12:00:00 #> 4 2007-11-19 18:00:00.000 10 2007-11-19 18:00:00 #> 5 2007-11-20 00:00:00.000 10 2007-11-20 00:00:00 mydf2$data_POSIX <- as.POSIXct(mydf2$data_POSIX, format = "%Y-%m-%d %H:%M:%S", tz="Etc/GMT-1") mydf2 #> date value data_POSIX #> 1 2007-11-19 00:00:00.000 10 2007-11-19 00:00:00 #> 2 2007-11-19 06:00:00.000 10 2007-11-19 06:00:00 #> 3 2007-11-19 12:00:00.000 10 2007-11-19 12:00:00 #> 4 2007-11-19 18:00:00.000 10 2007-11-19 18:00:00 #> 5 2007-11-20 00:00:00.000 10 2007-11-20 00:00:00 Also, since you are writing to and reading from a CSV file, use write.csv and read.csv. write.csv(mydf, file="mydf.txt", row.names=FALSE, quote=FALSE) mydf2 <- read.csv(file="mydf.txt") Hope this helps, Rui Barradas