This question already has answers here:
Converting year and month ("yyyy-mm" format) to a date?
(9 answers)
Closed 4 years ago.
I am trying to convert character strings to Dates in R. These are examples of the character strings:
"Aug-1973" "Aug-1974" "Aug-1975" "Aug-1976" "Aug-1977"
I run the following line on date strings similar to the ones above:
exportsDF$Date <- as.Date(as.character(exportsDF$Date), format = "%b-%Y")
This returns NAs for all values. The step where I convert the dates column to characters returns the correct values. Any ideas why the as.Date() command is not working? There are no NAs or missing values in the data. Every value has a "%b-%Y" format.
Any help is appreciated!
The date format needs a day as well, so you could add an arbitrary day of the month. Here, I've chosen the first day:
dates <- c("Aug-1973", "Aug-1974", "Aug-1975", "Aug-1976", "Aug-1977")
res <- as.Date(paste0("01-", dates), format = "%d-%b-%Y")
print(res)
#[1] "1973-08-01" "1974-08-01" "1975-08-01" "1976-08-01" "1977-08-01"
The reason is that the underlying Date data type is an integer counting the days since some reference day. Specifically, the number of days since 1970-01-01. See ?Date.
The Date object res can now be displayed as you please via
format(res, "%B-%Y")
#[1] "August-1973" "August-1974" "August-1975" "August-1976" "August-1977"
or similar.
The month(res) function and its cousins are also helpful. See ?month.
Related
This question already has answers here:
strptime, as.POSIXct and as.Date return unexpected NA
(2 answers)
Changing date format in R
(7 answers)
Closed 1 year ago.
I have a column in a dataframe which contains dates eg:
Date <- as.Date("2012-12-01 00:00:00")
Note: the actual dataframe format is "unknown"
I want to subset the month, date, hour from this dataframe and used this code
dmH <- as.POSIXct(Date, format="%Y%m%d %H%M%s")
dmH <- format(dmH, format="%m%d %H%M%s")
which returns a character format as below
"1201 02001354320000"
During this process it changed from UTC to EET so it starts at 02:00:00 and I don't know how to omit this change.
Most importantly, I need to have it in date format to be able to use it in a ggplot but I wasn't able to find any way to convert it, no matter what and how I tried.
EDIT:
As #Cath mentioned in the comment I tried to use that code but as.Date function returns only the year, month, day without the time. As a result, when I then try format function for any other time of the day it returns "00".
As opposed to as.Date I used again as.POSIXct and now it returns the right format (since I used the hyphen and %S in the "format" argument as you recommended). But still this is in character format which I need in date format.
So I used again mdH <- as.POSIXct(mdH, format = "%m-%d %H:%M:%S") on the formatted dataframe(mdH) as well as strptime to change it to date format but both return also the current year.
Note that if I use directly dmH <- strptime(as.character(Date), format="%m-%d %H:%M:%S") (as in one of the threads you recommended) it returns NA. Am I missing something? I can't resolve my issue
This question already has answers here:
Format date as Year/Quarter
(10 answers)
Closed 2 years ago.
In one of my columns I am given a date. I am trying to make a new column to indicate which quarter that date lies in so that way i can determine how many observations entered a certain venue in each quarter. End goal is to sumarize based off of quarter. Here is an example of the code I am using and an example of the output. as.Date(as.yearqtr(x, format ="%Y-%m-%d" )) . As you can see my problem is that It only returns 2019 q2, and i am confused why. This is my code PARTIES$QUARTER <- (as.yearqtr(PARTIES$opened, format = "%Y-%M-%d"))
It should be %m for (month) and not %M (which specifies the Minute as decimal number (00–59).)
library(zoo)
PARTIES$QUARTER <- as.yearqtr(PARTIES$opened, format = "%Y-%m-%d")
This question already has answers here:
How to convert date to format "yyyy-mm-dd" in R when input value can be of different formats
(3 answers)
Change Date print format from yyyy-mm-dd to dd-mm-yyyy
(2 answers)
Closed 2 years ago.
I need to find the difference in days between 2 date columns, but one of them is in the format of "6/16/2019" and the other is in the format of "2019-02-25". Not sure which one would be easier to convert to which, but would like to get end result in days. Which I know how to do. I would appreciate help converting the second yyyy-mm-dd to mm-dd-yyyy.
We can use functions from the lubridate package to convert the different formats to dates, and then subtract.
rawData <- "date1,date2
2002-05-15,6/16/2019
2019-12-31,4/15/2020"
data <- read.csv(text = rawData,stringsAsFactors = FALSE)
library(lubridate)
mdy(data$date2) - ymd(data$date1)
...and the output:
> mdy(data$date2) - ymd(data$date1)
Time differences in days
[1] 6241 106
>
This question already has answers here:
Converting year and month ("yyyy-mm" format) to a date?
(9 answers)
Closed 3 years ago.
I have encountered a difficulty, trying to use the as.Date function (in R) on a data frame to preserve date format. The date column consists of blank cells (i.e. missing dates) and observed dates in the format month/year (e.g. 8/2019).
As mentioned earlier, I have tried using the as.Date function but the column for the dates turns blank completely (i.e. no dates are reported). Below is the code I am using:
df$date <- df$date<- as.Date(df$date, format='%m/%Y') #df is the data frame
The expected results should have the observed dates and the missing dates replaced with NA. I greatly appreciate your help.
You need to add a date component to make it a complete date. Once you do that it is easy to convert it into an actual date object
as.Date(paste0("1/", "8/2019"), "%d/%m/%Y")
#[1] "2019-08-01"
Or using dmy from lubridate
lubridate::dmy(paste0("1/", "8/2019"))
This question already has answers here:
How to convert a character string date to date class if day value is missing
(1 answer)
Converting year and month ("yyyy-mm" format) to a date?
(9 answers)
Closed 6 years ago.
So I've been through some Stack Exchange answers, and I can't resolve this.
I have a column in a dataframe that has dates as characters as follows
2011-12
2012-04
2011-10
etc
I would like to convert these to date formats which I have tried to do as follows:
Tots$DatesMerge<-as.Date(Tots$DatesMerge,"%Y-%m")
but I get NA's back all the time.
I tried to do as here but no joy. I'm really not sure what I'm doing wrong.
I'd say as.Date won't be able to work on values where there's no day of the month. You could try with zoo, as long as you don't mind it coming out as a yearmon class:
library( zoo )
as.yearmon( Tots$DatesMerge )
Alternatively, you can specify a day of the month to use as a dummy:
as.Date( paste0( Tots$DatesMerge, "-15" ) )
Edit: there is already an answer and it is a duplicate, but I suppose the explanation can be useful for further readers, so I'll leave it.
Explanation
This comes from the documentation in R, "Dates are represented as the number of days since 1970-01-01, with negative values for earlier dates".
In R, dates are thus dependent on year, month and days or at least an integer that represent the span (in days) from or to 1970-01-01. As such, the base Dates package in R cannot convert the data formated in years and month into dates since there are no days.
Solution
As a consequence, you have the option, if you go with the base R package, to provide a a day that would be used to convert your data.
Tots$DatesMerge <- as.Date(paste0(Tots$DatesMerge,"01"),"%Y-%m-%d")