Date
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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