Message-ID: <0f3dcf3f-6edd-796c-5f34-9dd3515a26c1@effectivedefense.org>
Date: 2021-11-04T23:25:37Z
From: Spencer Graves
Subject: Date
In-Reply-To: <814a72360bbc4c5ab55c53da7588e0ec@SRVEXCHCM1302.precheza.cz>
My speculation is that Microsoft Excel recognized that as a date and
saved it in the "mm/dd/YYYY" format you saw when reading it into R with
dat=read.csv("myfile.csv").
"str" told you the format. You can convert that from character to
Date using as.Date(dat$mydate, '%m/%d/%Y'), as documented in
help('as.Date').
NOTE: The error message, "character string is not in a standard
unambiguous format" is almost appropriate: In this case, it's clear
that "09/16/2019" refers to month 09, day 16, and year 2019. However,
if it were "09/06/2019", we would not know if it were September 6 or 9
June of 2019. If it were "09/06/08", we would have the added
possibility with the year first, followed by month and day: June 8,
2009. This ambiguity is resolved most forcefully by ISO 8601.
Hope this helps.
Spencer Graves
On 11/4/21 5:30 PM, PIKAL Petr wrote:
> Hi
>
> Not sure why the date format was changed but if I am correct R do not read dates as dates but as character vector. You need to transfer such columns to dates by asDate. The error is probably from your use two asDate commands.
>
> Cheers
> Petr
> -----Original Message-----
> From: R-help <r-help-bounces at r-project.org> On Behalf Of Val
> Sent: Thursday, November 4, 2021 10:43 PM
> To: r-help at R-project.org (r-help at r-project.org) <r-help at r-project.org>
> Subject: [R] Date
>
> IHi All, l,
>
> I am reading a csv file and one of the columns is named as "mydate"
> with this form, 2019-09-16.
>
> I am reading this file as
>
> dat=read.csv("myfile.csv")
> the structure of the data looks like as follow
>
> str(dat)
> mydate : chr "09/16/2019" "02/21/2021" "02/22/2021" "10/11/2017" ...
>
> Please note the format has changed from YYYY-mm-dd to mm/dd/YYYY
> When I tried to change this as a Date using
>
> as.Date(as.Date(mydate, format="%m/%d/%Y" )
> I am getting this error message
> Error in charToDate(x) :
> characte string is not in a standard unambiguous format
>
> My question is,
> 1. how can I read the file as it is (i.e., without changing the date format) ?
> 2. why does R change the date format?
>
> Thank you,
>
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> PLEASE do read the posting guide http://www.R-project.org/posting-guide.html
> and provide commented, minimal, self-contained, reproducible code.
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