I wish to import my csv file into a data frame but the date in my csv file is in a non-standard format.
The date in the first column is in the following format:
08.09.2016
One of the arguments in my read.csv2 functions is to specify the classes and when I specify this column as a date I receive the following error upon execution:
Error in charToDate(x) :
character string is not in a standard unambiguous format
I'm guessing it doesn't like converting the date from factor class to date class.
I've read a little about POSIXlt but I don't understand the details of the function.
Any ideas how to convert the class from factor to date??
When you convert character to date, you need specify format if it is not standard. The error you got is the result of as.Date("08.09.2016"). But if you do as.Date("08.09.2016", format = "%m.%d.%Y"), it is fine.
I am not sure whether it is possible to pass format to read.csv2 for correct date formatting (maybe not). I would simply read in this date column as factor, then do as.Date(as.character(), format = "%m.%d.%Y") on this column myself.
Generally we use the following format "dd/mm/yy" how can I reorganise the date to that format?
Use format(, format = "%d/%m/%y").
A complete example:
format(as.Date("08.09.2016", format = "%m.%d.%Y"), format = "%d/%m/%y")
# [1] "09/08/16"
Related
I have an excel spreadsheet that has different date formats. R reads in the dates correctly when they're formatted as m/dd/yy, but when they're m/d/yy, it reads them as a code like this: 36251.
To fix it, I found this, which seems useful, but it is only for one date and I have multiple.
How to convert Excel date format to proper date in R
This was what was suggested:
as.Date(42705, origin = "1899-12-30")
So I tried this:
stockindices0$Date <- as.Date(stockindices0$Date , origin = "12-30-99")
but got the error:
Error in charToDate(x) :
character string is not in a standard unambiguous format
I also tried it with the year as 1899 with no success.
You can try this
as.Date(stockindices0$Date, format = "%d/%m/%y")
I would like to write DateTime values to an excel sheet using openxlsx. When I try to do this, instead of just the DateTime value, I get a lowercase "x" on one row followed by the DateTime in the subsequent row. This occurs whether I use write.xlsx or writeData. I also tried converting the DateTime using as.POSIXlt or as.POSIXct, converting the date with timezone specified or not, and get the same result.
The UTC DateTime values are coming from a PerkinElmer microplate reader file.
Below is a code snippet that gives me this result. Any advice or help is appreciated, Thanks!
library(openxlsx)
library(lubridate)
date <- as_datetime("2022-04-07T22:15:08+0000", tz = "America/Los_Angeles")
options(openxlsx.datetimeFormat = "yyyy-mm-dd hh:mm:ss")
write.xlsx(date,"test.xlsx",overwrite = TRUE)
The documentation of write.xlsx says in section Arguments that x is (my emphasis)
A data.frame or a (named) list of objects that can be handled by writeData() or writeDataTable() to write to file.
So apparently an atomic vector is first coerced to data.frame and since the data argument name is x, so is its column header.
This also happens when writing a named list date_list <- list(date = date). A workbook with a sheet named date is created and the data in it has a column header x.
I'm trying to convert a string into a date format "yyy-mm-dd" in R programming using below steps:
date<- as.Date(S, "%Y- %m- %d")
where S is a vector containing a string value "15082022"
But above method is not giving an output in the format yyy-mm-dd.
Can someone advise the correct command for this
The as.Date() function will convert a string into date format, and the format of the output will always be in yyyy-mm-dd format in R (ISO 8601). The format argument in the as.Date() function is to specify the date format of the string input. I remember I initially thought it was specifying the output format, but it's the input format (you can change the output format with a subsequent format() function, however this will convert it back to a string).
Your string looks to be in ddmmyyyy (%d%m%Y) format, this should be what you specify as the format argument in as.Date(). Your format does not include hyphens, so the format argument should also not include hyphens. Note that ddmmyyyy, dd-mm-yyyy, dd/mm/yyyy, dd.mm.yyyy are all different date formats, even though the day, month and year are in the same order, they would be converted to date with formats %d%m%Y, %d-%m-%Y, %d/%m/%Y, and %d.%m.%Y, respectively.
Further advice on working with dates and times is available in the relevant chapters of R for Data Science by Wickham & Grolemund and The R Cookbook by Teetor & Long.
I read a .xlsx file containing Date columns into R and converted it into dataframe.
Some date columns are being read correctly but most of the others are getting converted to "43116" format.
Any attempt to convert it into Date using as.Date(, origin= <>, format=<>) is returning NA.
I have tried all possible solutions like using 'stringAsFactors = FALSE', POSIT thing and checking the excel file for date formats but nothing worked.
Please help.
It is difficult to recreate the problem if no data is provided, but if you want to convert the number 43129 or the character "43129" to a R date you should do the following:
a <- 43129
b <- '43129'
format(as.Date(a, origin = "1899-12-30"), '%Y-%m-%d')
[1] "2018-01-29"
format(as.Date(as.integer(b), origin = "1899-12-30"), '%Y-%m-%d')
[1] "2018-01-29"
I used the format yyyy-mm-dd, but any other date format could be used if you format it properly.
Hope it helps!
I have a dataset called EPL2011_12. I would like to make new a dataset by subsetting the original by date. The dates are in the column named Date The dates are in DD-MM-YY format.
I have tried
EPL2011_12FirstHalf <- subset(EPL2011_12, Date > 13-01-12)
and
EPL2011_12FirstHalf <- subset(EPL2011_12, Date > "13-01-12")
but get this error message each time.
Warning message:
In Ops.factor(Date, 13- 1 - 12) : > not meaningful for factors
I guess that means R is treating like text instead of a number and that why it won't work?
Well, it's clearly not a number since it has dashes in it. The error message and the two comments tell you that it is a factor but the commentators are apparently waiting and letting the message sink in. Dirk is suggesting that you do this:
EPL2011_12$Date2 <- as.Date( as.character(EPL2011_12$Date), "%d-%m-%y")
After that you can do this:
EPL2011_12FirstHalf <- subset(EPL2011_12, Date2 > as.Date("2012-01-13") )
R date functions assume the format is either "YYYY-MM-DD" or "YYYY/MM/DD". You do need to compare like classes: date to date, or character to character. And if you were comparing character-to-character, then it's only going to be successful if the dates are in the YYYYMMDD format (with identical delimiters if any delimiters are used).
The first thing you should do with date variables is confirm that R reads it as a Date. To do this, for the variable (i.e. vector/column) called Date, in the data frame called EPL2011_12, input
class(EPL2011_12$Date)
The output should read [1] "Date". If it doesn't, you should format it as a date by inputting
EPL2011_12$Date <- as.Date(EPL2011_12$Date, "%d-%m-%y")
Note that the hyphens in the date format ("%d-%m-%y") above can also be slashes ("%d/%m/%y"). Confirm that R sees it as a Date. If it doesn't, try a different formatting command
EPL2011_12$Date <- format(EPL2011_12$Date, format="%d/%m/%y")
Once you have it in Date format, you can use the subset command, or you can use brackets
WhateverYouWant <- EPL2011_12[EPL2011_12$Date > as.Date("2014-12-15"),]