I am trying to parse a string representing a period consisting of minutes, seconds, and milliseconds. My preferred functions for this would come from the readr package, where seconds and milliseconds may be seen jointly as partial seconds. Apparently, within this package there is a silent assumption that minutes are represented as two digits, i.e. padded with zeros.
readr::parse_time("1:23.456", format="%M:%OS") # doesn't work
readr::parse_time("01:23.456", format="%M:%OS") # works
The ms function from lubridate handles this straight out of the box:
lubridate::ms("1:23.456")
Any workaround for this so I can use parse_time and other functions in readr without resorting to pad with zeros myself?
The format specifications can be shown here:
https://stat.ethz.ch/R-manual/R-devel/library/base/html/strptime.html and
https://readr.tidyverse.org/reference/parse_datetime.html
The issue here is that %M refers to the time shown in minutes between "00" and "99". Note that this is the exact specification that you passed so it is part of the specified format rather than an assumption of the package. As far as I'm aware there is no minutes argument that accepts varying string lengths that can be passed to the format column. (This is dissimilar to the day argument which would accept a single character).
Lubridate's ms function uses a different method to parse time strings. Lubridate's function is far more robust due to being able to handle many formats of times including the one specified in the question when no format is given.
Related
I am using the read.xlsx function in R to read excel sheets. All the values of a date column 'A' is of the form dd/mm/yyyy. However,when using the read.xlsx function, the values of the date parsed ranges from being an integer ie. 42283 to string i.e. 20/08/2015. This probelm persist even when I uses read.xlsx2.
I guess the inconsistency in the format for different rows makes it hard to change the column to a single standard format. Also, it is hard to specify the column classes in the read.xlsx since I have more than 100 variables.
Are there ways around this problem and also is this an excel specific problems?
Thank you!
This problem with date formats is pervasive and it seems like every R package out there deals with it differently. My experience with read.xlsx has been that it sometimes saves the date as a character string of numbers, e.g. "42438" as character data that I then have to convert to numeric and then to POSIXct. Then other times, it seems to save it as numeric and sometimes as character and once in a while, actually as POSIXct! If you're consistently getting character data in the form "20/08/2015", try the lubridate package:
library(lubridate)
dmy("20/08/2015")
I have a vector that contains time data, but there's a problem: some of the entries are listed as dates (e.g., 10/11/2017), while other entries are listed as dates with time (e.g., 12/15/2016 09:07:17). This is problematic for myself, since as.Date() can't recognize the time portion and enters dates in an odd format (0012-01-20), while seemingly adding dates with time entries as NA's. Furthermore, using as.POSIXct() doesn't work, since not all entries are a combination of date with time.
I suspect that, since these entries are entered in a consistent format, I could hypothetically use an if function to change the entries in the vector to a consistent format, such as using an if statement to remove time entirely, but I don't know enough about it to get it to work.
use
library(lubridate)
Name of the data frame or table-> x
the column that has date->Date
use the ymd function
x$newdate<-ydm(x$Date)
I don't understand why this doesn't work:
as.Date('2001-10-26 10:00:00', format='%Y-%m-%d %H:%M:%S')
It returns
"2001-10-26"
but I expected it to be
"2001-10-26 10:00:00".
I don't need anything complicated; just to convert a string to a date with a timestamp. Not sure why the format argument isn't working.
Thanks.
R has several ways (expressed in classes) to deal with time and dates. In your fist code you are using the as.Date function that converts its arguments to Date class. The string you are providing to that function contains also other elements that do not belong to Date class and as a result it prints only elements that the function is allowed to handle. As you can read in the documentation:
... (dates)... They are always printed following the rules of the current Gregorian
calendar, even though that calendar was not in use long ago (it was
adopted in 1752 in Great Britain and its colonies).
the informations are essentially lost.
See here:
a <- as.Date('2001-10-26 10:00:00', format='%Y-%m-%d %H:%M:%S')
format(a, format='%Y-%m-%d %H:%M:%S')
[1] "2001-10-26 00:00:00"
If you want to keep informations about the time and not only the dates you have to use a format that is able to store that informations. The classes are POSIXct and POSIXlt where the first one is just a huge integer that counts the seconds since 1970-01-01 and the second one is just a list where each element stores seconds, days, months etc.
The functions (in base R) you have to use are: strptime (as pointed out in comments by #nongkrong), or as.POSIXlt or as.POSIXct.
There are other functions in other packages (like chron and lubridate) but putting aside special classes developed by single packages (like period in lubridate) the key classes are the ones I've just illustrated here.
As a new and self taught R user I am struggling with converting date and time values characters into numbers to enable me to group unique combinations of data. I'm hoping someone has come across this before and knows how I might go about it.
I'd like to convert a field of DateTime data (30/11/2012 14:35) to a numeric version of the date and time (seconds from 1970 maybe??) so that I can back reference the date and time if needed.
I have search the R help and online help and only seem to be able to find POSIXct, strptime which seem to convert the other way in the examples I've seen.
I will need to apply the conversion to a large dataset so I need to set the formatting for a field not an individual value.
I have tried to modify some python code but to no avail...
Any help with this, including pointers to tools I should read about would be much appreciated.
You can do this with base R just fine, but there are some shortcuts for common date formats in the lubridate package:
library(lubridate)
d <- ymd_hms("30/11/2012 14:35")
> as.numeric(d)
[1] 1921407275
From ?POSIXct:
Class "POSIXct" represents the (signed) number of seconds since the
beginning of 1970 (in the UTC timezone) as a numeric vector.
I have a vector of times in R, all_symbols$Time and I am trying to find out how to get JUST the times (or convert the times to strings without losing information). I use
strptime(all_symbol$Time[j], format="%H:%M:%S")
which for some reason assumes the date is today and returns
[1] "2013-10-18 09:34:16"
Date and time formatting in R is quite annoying. I am trying to get the time only without adding too many packages (really any--I am on a school computer where I cannot install libraries).
Once you use strptime you will of necessity get a date-time object and the default behavior for no date in the format string is to assume today's date. If you don't like that you will need to prepend a string that is the date of your choice.
#James' suggestion is equivalent to what I was going to suggest:
format(all_symbol$Time[j], format="%H:%M:%S")
The only package I know of that has time classes (i.e time of day with no associated date value) is package:chron. However I find that using format as a way to output character values from POSIXt objects lends itself well to functions that require factor input.
In the decade since this was written there is now a package named “hms” that has some sort of facility for hours, minutes, and seconds.
hms: Pretty Time of Day
Implements an S3 class for storing and formatting time-of-day values, based on the 'difftime' class.
Came across the same problem recently and found this and other posts R: How to handle times without dates? inspiring. I'd like to contribute a little for whoever has similar questions.
If you only want to you base R, take advantage of as.Date(..., format = ("...")) to transform your date into a standard format. Then, you can use substr to extract the time. e.g. substr("2013-10-01 01:23:45 UTC", 12, 16) gives you 01:23.
If you can use package lubridate, functions like mdy_hms will make life much easier. And substr works most of the time.
If you want to compare the time, it should work if they are in Date or POSIXt objects. If you only want the time part, maybe force it into numeric (you may need to transform it back later). e.g. as.numeric(hm("00:01")) gives 60, which means it's 60 seconds after 00:00:00. as.numeric(hm("23:59")) will give 86340.