I've tried everything in this thread as.Date returning NA while converting from 'ddmmmyyyy' to try and sort my problem.
I'm using these commands to turn a factor into a date:
cohort$doi <- as.Date(cohort$doi, format= "%Y/%m/%d")
All my dates are currently in the format: YYYY-MM-DD, so as far as I'm aware the above should work
I used this code yesterday to convert all my dates for various variables from a factor to a date. It worked yesterday and everything was fine. Today I opened my script and imported in my data, ran this command and viewed my data but all of the dates now say NA.
I've tried everything from previous threads (I looked at a few more than just the one I linked above) but nothing has so far worked. I'm not sure what to do now
Example of what doi column looks like:
1970-01-01
1970-02-02
1970-03-03
1970-04-04
The column is currently classed as an factor. And when I do the code I used above, the column is defined as a date but all the dates now say NA
Other than closing R and opening it up again for today, I've done nothing else.
If you read the documentation for as.Date you will note the default format is %Y-%d-%m or %Y/%d/%m:
The default formats follow the rules of the ISO 8601 international standard which expresses a day as "2001-02-03".
In your code you have specified your dates are formatted by slashes, but your sample data shows they are formatted in the default format used by as.Date:
doi <- as.factor(c("1970-01-01",
"1970-02-02",
"1970-03-03",
"1970-04-04"))
as.Date(doi) # default format %Y-%m-%d
[1] "1970-01-01" "1970-02-02" "1970-03-03" "1970-04-04"
as.Date(doi, format = "%Y/%m/%d") # incorrect specification of your date format
[1] NA NA NA NA
as.Date("1970/01/01") # also a default format
[1] "1970-01-01"
Note: as.Date accepts character strings, factors, logical NA and objects of classes "POSIXlt" and "POSIXct".
Related
I'm having trouble formatting a list of dates in R. The conventional methods of formatting in R such as as.Date or as.POSIXct don't seem to be working.
I have dates in the format: 1012015
using
as.POSIXct(as.character(data$Start_Date), format = "%m%d%Y")
does not give me an error, but my date returns
"0015-10-12" because the month is not a two digit number.
Is there a way to change this into the correct date format?F
The lubridate package can help with this:
lubridate::mdy(1012015)
[1] "2015-01-01"
The format looks ambiguous but the OP gave two hints:
He is using format = "%m%d%Y" in his own attempt, and
he argues the issue is because the month is not a two digit number
This uses only base R. The %08d specifies a number to be formatted into 8 characters with 0 fill giving in this case "01012015".
as.POSIXct(sprintf("%08d", 1012015), format = "%m%d%Y")
## [1] "2015-01-01 EST"
Note that if you don't have any hours/minutes/seconds it would be less error prone to use "Date" class since then the possibility of subtle time zone errors is eliminated.
as.Date(sprintf("%08d", 1012015), format = "%m%d%Y")
## [1] "2015-01-01"
I'm currently working my way through the adehabitatLT package.
I've put my date_time column into characters and named it da:
da<-as.character(dat$date_time)
head(da)
[1] "7/08/2015 0:22" "7/08/2015 0:52" "7/08/2015 1:22" "7/08/2015 1:52" "7/08/2015 2:56" "7/08/2015 3:26"
As you can see my date_time input is a bit non traditional and i think this is where the error occurs, because when i create the class POSIXct:
da<-as.POSIXct(strptime(as.character(dat$date_time),"%d/%m/%y% H:%M:%S"))
It creates the class but i get NA for all my values:
head(da)
[1] NA NA NA NA NA NA
My end objective here is to create an object of the class ltraj (but not only containing the date but the time as well).
Any ideas anyone?
Kind regards,
Sam
da<-as.POSIXct(strptime(as.character(locs$Date),"%y%m%d"))
The format should be modified to
as.POSIXct(strptime(da, "%d/%m/%Y %H:%M"))
Or if month is first followed by day, then change it to "%m/%d/%Y %H:%M"
While parsing tricky date/time formats, it might be useful to use lubridate package by Garrett Grolemund and Hadley Wickham.
In your case, simply do
require(lubridate)
a <- dmy_hm(da)
The separator and the number of digits for day or month or hours etc are automatically parsed.
Find more info here
I'm importing time series data from a CSV file and one of the vectors/columns are dates in the format DD/MM/YYYY. Vector class is characters or factors if I chose the Strings as factors = True. I convert the imported file to a data frame and then run the following:
df$Date <- as.Date(df$Date , "%d/%m/%y")
I get no error message, but the dates are all messed up in the format YYYYMMDD and all the YYYY are the year 2020...
Before:
10/09/2009
11/09/2009
14/09/2009
After:
2020-09-10
2020-09-11
2020-09-14
You are using %y when it should be %Y. See the documentation here.
%y
Year without century (00–99). On input, values 00 to 68 are prefixed by 20 and 69 to 99 by 19 – that is the behaviour specified by the 2004 and 2008 POSIX standards, but they do also say ‘it is expected that in a future version the default century inferred from a 2-digit year will change’.
%Y
Year with century. Note that whereas there was no zero in the original Gregorian calendar, ISO 8601:2004 defines it to be valid (interpreted as 1BC): see http://en.wikipedia.org/wiki/0_(year). Note that the standards also say that years before 1582 in its calendar should only be used with agreement of the parties involved.
Try running the code again so that the data frame is not modified by any previous attempt but this time use
df$Date <- as.Date(df$Date , "%d/%m/%Y")
#Heroka is right.
If ever you need it you could also use posixct objects (they contain information of seconds)
Try this:
df$Date.time <- as.POSIXct(df$Date , format="%d/%m/%Y")
If you want the date and time in strings you can try the following:
df$Date.time <- format(as.POSIXct(df$Date , format="%d/%m/%Y"),format="%Y-%m-%d %H:%M")
or
df$Date <- format(as.POSIXct(df$Date , format="%d/%m/%Y"),format="%Y-%m-%d")
I am trying to change my date within my dataframe into the correct format within R. (m/d/y to the correct yyyy-mm-dd).
I have data that looks like this
Date Time pH
1 1/4/1981 9:00 3.9
2 1/8/1981 8:30 3.9
etc
The name of my data frame I am working in is data.cat.AC
I tried
data.cat.AC[,1]$Date <- as.Date(data.cat.AC[,1]$Date, "%Y/%m/%d")
...but this did not work.
I am getting the error,
$ operator is invalid for atomic vectors
Any tips or pointers on what I am doing wrong?
When you use as.Date, you should not enter the format that you want as output. Instead enter the format as it is in the data.
as.Date("1/4/1981", format="%m/%d/%Y")
[1] "1981-01-04"
We got lucky in this case in that your desired output happens to be the default output. But for learning purposes, let's say you wanted the format "dd:mm:YYYY". After converting to Date format as we did above, we would use:
format(x2, "%m:%d:%Y")
[1] "01:04:1981"
I have a data set in R that contains a column of dates in the format yyyy/mm/dd. I am trying to use as.Date to convert these dates to date objects in R. However, I cannot seem to find the correct argument for origin to input into as.Date. The following code is an example of what I have been trying. I am using a CSV file from Excel, so I used origin="1899/12/30 based on other sites I have looked at.
> as.Date(2001/04/26, origin="1899/12/30")
[1] "1900-01-18"
However, this is not working since the input date 2001/04/26 is returned as "1900-01-18". I need to convert the dates into date objects so I can then convert the dates into julian dates.
You can either is as.Date with a numeric value, or with a character value. When you type just 2001/04/26 into R, that's doing division and getting 19.24 (a numeric value). And numeric values require an origin and the number you supply is the offset from that origin. So you're getting 19 days away from your origin, ie "1900-01-18". A date like Apr 26 2001 would be
as.Date(40659, origin="1899-12-30")
# [1] "2011-04-26"
If your dates from Excel "look like" dates chances are they are character values (or factors). To convert a character value to a Date with as.Date() you want so specify a format. Here
as.Date("2001/04/26", format="%Y/%m/%d")
# [1] "2001-04-26"
see ?strptime for details on the special % variables. Now if you're read your data into a data.frame with read.table or something, there's a chance your variable may be a factor. If that's the case, you'll want do convert to character with'
as.Date(as.character(mydf$datecol), format="%Y/%m/%d")